Do not parse collections' description in the overview
The description of each collection as shown in the collections list should not be parsed - it looks confusing and ugly (see "Autotools in SCL" in Autotools in the attached image). This applies also to horizontal lines (see "Questions/Support" in Php54more).

Thanks for noticing. I know about that lines - it is bug and I'm going to fix it.
About that heading in the description, I have to agree with you. We should allow (or display) only normal text in the preview description.
I disagree. I agree that Autotools description looks ugly. But you have markdown syntax available and it is up to each maintainer what he will do with that. There are usefull things like lists, links, which people otherwise missed and asked for that in past.
Sorry for not being clear in my previous comment. I wanted to say that we should allow the short text description in the list of all collections only. The collection detail however, would stay untouched with all the details, headings, links and other stuff that maintainer choose and users asked for.