@nathantypanski explained earlier, and I have to agree:
To add my own:
- Most implementations of ReST I've seen do a very bad job of telling you where and why your ReST is not working. Mostly, they just give you some semi-broken output.
I'm also going to say that AsciiDoc is looking pretty good to me, too - it looks much less finicky than ReST, except perhaps for tables (which seem to be hard in any markup language), and it also has a large set of the features we're looking for, unlike Markdown.
I also just read the Wikipedia article on it, and apparently "Most of the Git documentation is written in AsciiDoc", not just Pro Git - so while it may not be as widespread as Markdown or ReST, but it does have some precedent.
Either way, it seems like whether or not we stick with Markdown for the foreseeable future, we may want to leave the door open for other options later on.