If HTML style comments contain headings they do not work

[feinstaub]

This is a Markdown sample which gets rendered unexpectedly. For this...

aaa
<!-- test
====
-->
bbb

...I would expect this HTML output:

aaa
bbb

But instead it looks like this:

[Feder1co5oave]

It seems we need to prioritize html blocks before setext headings.

babelmark