Maciej Brencz, thanks for updating me! Maciej told me that Mike Schwartz from Wikia recently added a list of Wikia's "test cases and situations we need to fallback to source mode":

http://www.mediawiki.org/wiki/Future/Parser_test_cases.

I'll put together a short description of how we handle parsing of wikitext to HTML and reverse parsing of HTML back to wikitext in our Rich Text Editor.

I hope that together we will make significant improvement to the MW Parser!

I hope so too, Maciej. Thanks!

Welcoming parser test cases from all interested parties; stick 'em on that page.