For an example see:
https://en.wikipedia.org/wiki/User:Amire80/heading-comment?veaction=edit
There is an HTML comment that begins after a heading.
This page is rendered correctly, but in the VE the heading is displayed incorrectly and there is a line break character after it.
This is a rather esoteric case, but such comments do happen. They are used in GSoC templates among other things; for an example see the "Deliverables" section heading at
https://www.mediawiki.org/w/index.php?title=User:Vikassy/GSoC14&oldid=931677
Version: unspecified
Severity: normal