(Nick Reinking nick@twoevils.org):
I'm actually in the middle of a C project to reduce the wikitext parser to a two-pass parser...
Don't stop working on it, but be aware that when our performance issues are lessened for a while, I plan to go back to some work I had been planning for a long time to simplify and formalize wikitext syntax while adding some powerful features to it, so make sure your code is open and modular enough that it can be changed.
The first plan was to unify link syntax; rather than having [http://xxx zzz] for external links and [[xxx|zzz]] for internals, I want to unify on [[xxx|zzz]] for both, and treat "http", "ftp", etc. as special namespaces that makes external links.
The ''''' thing has /never/ worked correctly, and still doesn't. Part of the problem is that there's no precise, formal definition of what it /should/ do, and no obvious "best" choice. I want to nail that down soon.
I really want to implement styles with the {{class}} syntax I detailed earlier. That will let HTML gurus produce effects that will be much easier for novices to edit than the current mess.
Finally, I want to do something about a wikitext syntax for tables, probably using || characters.