diff --git a/scalastyle-config.xml b/scalastyle-config.xml
index f52b09551add..d6f927b6fa80 100644
--- a/scalastyle-config.xml
+++ b/scalastyle-config.xml
@@ -14,25 +14,41 @@
   ~ See the License for the specific language governing permissions and
   ~ limitations under the License.
   -->
-<!-- If you wish to turn off checking for a section of code, you can put a comment in the source
- before and after the section, with the following syntax: -->
-<!-- // scalastyle:off -->
-<!-- ... -->
-<!-- // naughty stuff -->
-<!-- ... -->
-<!-- // scalastyle:on -->
+<!--
+
+If you wish to turn off checking for a section of code, you can put a comment in the source
+before and after the section, with the following syntax:
+
+  // scalastyle:off
+  ...  // stuff that breaks the styles
+  // scalastyle:on
+
+You can also disable only one rule, by specifying its rule id, as specified in:
+  http://www.scalastyle.org/rules-0.7.0.html
+
+  // scalastyle:off no.finalize
+  override def finalize(): Unit = ...
+  // scalastyle:on no.finalize
+
+This file is divided into 3 sections:
+ (1) rules that we enforce.
+ (2) rules that we would like to enforce, but haven't cleaned up the codebase to turn on yet
+     (or we need to make the scalastyle rule more configurable).
+ (3) rules that we don't want to enforce.
+-->
 
 <scalastyle>
- <name>Scalastyle standard configuration</name>
- <check level="error" class="org.scalastyle.file.FileTabChecker" enabled="true"></check>
- <!-- <check level="error" class="org.scalastyle.file.FileLengthChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maxFileLength"><![CDATA[800]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <check level="error" class="org.scalastyle.file.HeaderMatchesChecker" enabled="true">
-  <parameters>
-   <parameter name="header"><![CDATA[/*
+  <name>Scalastyle standard configuration</name>
+
+  <!-- ================================================================================ -->
+  <!--                               rules we enforce                                   -->
+  <!-- ================================================================================ -->
+
+  <check level="error" class="org.scalastyle.file.FileTabChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.file.HeaderMatchesChecker" enabled="true">
+    <parameters>
+       <parameter name="header"><![CDATA[/*
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -48,122 +64,164 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */]]></parameter>
-  </parameters>
- </check>
+    </parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.SpacesAfterPlusChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.SpacesBeforePlusChecker" enabled="true"></check>
 
   <check level="error" class="org.scalastyle.file.WhitespaceEndOfLineChecker" enabled="true"></check>
 
- <check level="error" class="org.scalastyle.scalariform.SpacesAfterPlusChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.scalariform.SpacesBeforePlusChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.file.WhitespaceEndOfLineChecker" enabled="false"></check>
- <check level="error" class="org.scalastyle.file.FileLineLengthChecker" enabled="true">
-  <parameters>
-   <parameter name="maxLineLength"><![CDATA[100]]></parameter>
-   <parameter name="tabSize"><![CDATA[2]]></parameter>
-   <parameter name="ignoreImports">true</parameter>
-  </parameters>
- </check>
- <check level="error" class="org.scalastyle.scalariform.ClassNamesChecker" enabled="true">
-  <parameters>
-   <parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter>
-  </parameters>
- </check>
- <check level="error" class="org.scalastyle.scalariform.ObjectNamesChecker" enabled="true">
-  <parameters>
-   <parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter>
-  </parameters>
- </check>
- <check level="error" class="org.scalastyle.scalariform.PackageObjectNamesChecker" enabled="true">
-  <parameters>
-   <parameter name="regex"><![CDATA[^[a-z][A-Za-z]*$]]></parameter>
-  </parameters>
- </check>
- <check level="error" class="org.scalastyle.scalariform.EqualsHashCodeChecker" enabled="false"></check>
- <!-- <check level="error" class="org.scalastyle.scalariform.IllegalImportsChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="illegalImports"><![CDATA[sun._,java.awt._]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <check level="error" class="org.scalastyle.scalariform.ParameterNumberChecker" enabled="true">
-  <parameters>
-   <parameter name="maxParameters"><![CDATA[10]]></parameter>
-  </parameters>
- </check>
- <!-- <check level="error" class="org.scalastyle.scalariform.MagicNumberChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="ignore"><![CDATA[-1,0,1,2,3]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <check level="error" class="org.scalastyle.scalariform.NoWhitespaceBeforeLeftBracketChecker" enabled="false"></check>
- <check level="error" class="org.scalastyle.scalariform.NoWhitespaceAfterLeftBracketChecker" enabled="false"></check>
- <!-- <check level="error" class="org.scalastyle.scalariform.ReturnChecker" enabled="true"></check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.NullChecker" enabled="true"></check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.NoCloneChecker" enabled="true"></check> -->
+  <check level="error" class="org.scalastyle.file.FileLineLengthChecker" enabled="true">
+    <parameters>
+      <parameter name="maxLineLength"><![CDATA[100]]></parameter>
+      <parameter name="tabSize"><![CDATA[2]]></parameter>
+      <parameter name="ignoreImports">true</parameter>
+    </parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.ClassNamesChecker" enabled="true">
+    <parameters><parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter></parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.ObjectNamesChecker" enabled="true">
+    <parameters><parameter name="regex"><![CDATA[[A-Z][A-Za-z]*]]></parameter></parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.PackageObjectNamesChecker" enabled="true">
+    <parameters><parameter name="regex"><![CDATA[^[a-z][A-Za-z]*$]]></parameter></parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.ParameterNumberChecker" enabled="true">
+    <parameters><parameter name="maxParameters"><![CDATA[10]]></parameter></parameters>
+  </check>
+
   <check level="error" class="org.scalastyle.scalariform.NoFinalizeChecker" enabled="true"></check>
+
   <check level="error" class="org.scalastyle.scalariform.CovariantEqualsChecker" enabled="true"></check>
- <!-- <check level="error" class="org.scalastyle.scalariform.StructuralTypeChecker" enabled="true"></check> -->
- <!-- <check level="error" class="org.scalastyle.file.RegexChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="regex"><![CDATA[println]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.NumberOfTypesChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maxTypes"><![CDATA[30]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.CyclomaticComplexityChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maximum"><![CDATA[10]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
 
   <check level="error" class="org.scalastyle.scalariform.StructuralTypeChecker" enabled="true"></check>
 
- <check level="error" class="org.scalastyle.scalariform.UppercaseLChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.scalariform.SimplifyBooleanExpressionChecker" enabled="false"></check>
- <check level="error" class="org.scalastyle.scalariform.IfBraceChecker" enabled="true">
-  <parameters>
-   <parameter name="singleLineAllowed"><![CDATA[true]]></parameter>
-   <parameter name="doubleLineAllowed"><![CDATA[true]]></parameter>
-  </parameters>
- </check>
- <!-- <check level="error" class="org.scalastyle.scalariform.MethodLengthChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maxLength"><![CDATA[50]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.MethodNamesChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="regex"><![CDATA[^[a-z][A-Za-z0-9]*$]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <!-- <check level="error" class="org.scalastyle.scalariform.NumberOfMethodsInTypeChecker" enabled="true"> -->
- <!--  <parameters> -->
- <!--   <parameter name="maxMethods"><![CDATA[30]]></parameter> -->
- <!--  </parameters> -->
- <!-- </check> -->
- <check level="error" class="org.scalastyle.scalariform.PublicMethodsHaveTypeChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.file.NewLineAtEofChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.file.NoNewLineAtEofChecker" enabled="false"></check>
- <check level="error" class="org.scalastyle.scalariform.NonASCIICharacterChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.scalariform.SpaceAfterCommentStartChecker" enabled="true"></check>
- <check level="error" class="org.scalastyle.scalariform.EnsureSingleSpaceBeforeTokenChecker" enabled="true">
+  <check level="error" class="org.scalastyle.scalariform.UppercaseLChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.IfBraceChecker" enabled="true">
+    <parameters>
+      <parameter name="singleLineAllowed"><![CDATA[true]]></parameter>
+      <parameter name="doubleLineAllowed"><![CDATA[true]]></parameter>
+    </parameters>
+  </check>
+
+  <check level="error" class="org.scalastyle.scalariform.PublicMethodsHaveTypeChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.file.NewLineAtEofChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.NonASCIICharacterChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.SpaceAfterCommentStartChecker" enabled="true"></check>
+
+  <check level="error" class="org.scalastyle.scalariform.EnsureSingleSpaceBeforeTokenChecker" enabled="true">
    <parameters>
      <parameter name="tokens">ARROW, EQUALS, ELSE, TRY, CATCH, FINALLY, LARROW, RARROW</parameter>
    </parameters>
- </check>
+  </check>
+
   <check level="error" class="org.scalastyle.scalariform.EnsureSingleSpaceAfterTokenChecker" enabled="true">
     <parameters>
      <parameter name="tokens">ARROW, EQUALS, COMMA, COLON, IF, ELSE, DO, WHILE, FOR, MATCH, TRY, CATCH, FINALLY, LARROW, RARROW</parameter>
     </parameters>
   </check>
+
+  <!-- ??? usually shouldn't be checked into the code base. -->
   <check level="error" class="org.scalastyle.scalariform.NotImplementedErrorUsage" enabled="true"></check>
+
   <!-- As of SPARK-7558, all tests in Spark should extend o.a.s.SparkFunSuite instead of FunSuite directly -->
-  <check level="error" class="org.scalastyle.scalariform.TokenChecker" enabled="true">
-   <parameters>
-    <parameter name="regex">^FunSuite[A-Za-z]*$</parameter>
-   </parameters>
-   <customMessage>Tests must extend org.apache.spark.SparkFunSuite instead.</customMessage>
+  <check customId="funsuite" level="error" class="org.scalastyle.scalariform.TokenChecker" enabled="true">
+    <parameters><parameter name="regex">^FunSuite[A-Za-z]*$</parameter></parameters>
+    <customMessage>Tests must extend org.apache.spark.SparkFunSuite instead.</customMessage>
+  </check>
+
+  <!-- ================================================================================ -->
+  <!--       rules we'd like to enforce, but haven't cleaned up the codebase yet        -->
+  <!-- ================================================================================ -->
+
+  <!-- SPARK-7977 We should turn this on, but we'd need to add whitelist to files that are using it first. -->
+  <check customId="println" level="error" class="org.scalastyle.scalariform.TokenChecker" enabled="false">
+    <parameters><parameter name="regex">^println$</parameter></parameters>
+    <customMessage><![CDATA[Are you sure you want to println? If yes, wrap the code block with
+      // scalastyle:off println
+      println(...)
+      // scalastyle:on println]]></customMessage>
+  </check>
+
+  <!-- We cannot turn the following two on, because it'd fail a lot of string interpolation use cases. -->
+  <!-- Ideally the following two rules should be configurable to rule out string interpolation. -->
+  <check level="error" class="org.scalastyle.scalariform.NoWhitespaceBeforeLeftBracketChecker" enabled="false"></check>
+  <check level="error" class="org.scalastyle.scalariform.NoWhitespaceAfterLeftBracketChecker" enabled="false"></check>
+
+  <!-- This breaks symbolic method names so we don't turn it on. -->
+  <!-- Maybe we should update it to allow basic symbolic names, and then we are good to go. -->
+  <check level="error" class="org.scalastyle.scalariform.MethodNamesChecker" enabled="false">
+    <parameters>
+    <parameter name="regex"><![CDATA[^[a-z][A-Za-z0-9]*$]]></parameter>
+    </parameters>
+  </check>
+
+  <!-- Should turn this on, but we have a few places that need to be fixed first -->
+  <check level="error" class="org.scalastyle.scalariform.EqualsHashCodeChecker" enabled="false"></check>
+
+  <!-- ================================================================================ -->
+  <!--                               rules we don't want                                -->
+  <!-- ================================================================================ -->
+
+  <check level="error" class="org.scalastyle.scalariform.IllegalImportsChecker" enabled="false">
+    <parameters><parameter name="illegalImports"><![CDATA[sun._,java.awt._]]></parameter></parameters>
   </check>
+
+  <!-- We want the opposite of this: NewLineAtEofChecker -->
+  <check level="error" class="org.scalastyle.file.NoNewLineAtEofChecker" enabled="false"></check>
+
+  <!-- This one complains about all kinds of random things. Disable. -->
+  <check level="error" class="org.scalastyle.scalariform.SimplifyBooleanExpressionChecker" enabled="false"></check>
+
+  <!-- We use return quite a bit for control flows and guards -->
+  <check level="error" class="org.scalastyle.scalariform.ReturnChecker" enabled="false"></check>
+
+  <!-- We use null a lot in low level code and to interface with 3rd party code -->
+  <check level="error" class="org.scalastyle.scalariform.NullChecker" enabled="false"></check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.scalariform.NoCloneChecker" enabled="false"></check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.file.FileLengthChecker" enabled="false">
+    <parameters><parameter name="maxFileLength">800></parameter></parameters>
+  </check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.scalariform.NumberOfTypesChecker" enabled="false">
+    <parameters><parameter name="maxTypes">30</parameter></parameters>
+  </check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.scalariform.CyclomaticComplexityChecker" enabled="false">
+    <parameters><parameter name="maximum">10</parameter></parameters>
+  </check>
+
+  <!-- Doesn't seem super big deal here ... -->
+  <check level="error" class="org.scalastyle.scalariform.MethodLengthChecker" enabled="false">
+    <parameters><parameter name="maxLength">50</parameter></parameters>
+  </check>
+
+  <!-- Not exactly feasible to enforce this right now. -->
+  <!-- It is also infrequent that somebody introduces a new class with a lot of methods. -->
+  <check level="error" class="org.scalastyle.scalariform.NumberOfMethodsInTypeChecker" enabled="false">
+    <parameters><parameter name="maxMethods"><![CDATA[30]]></parameter></parameters>
+  </check>
+
+  <!-- Doesn't seem super big deal here, and we have a lot of magic numbers ... -->
+  <check level="error" class="org.scalastyle.scalariform.MagicNumberChecker" enabled="false">
+    <parameters><parameter name="ignore">-1,0,1,2,3</parameter></parameters>
+  </check>
+
 </scalastyle>