On Wikisophia it works: http://wikisophia.org/wiki/User:Hillgentleman
We're using a superset of AMS-LaTeX, HillGentleman, which may be available on Wikipedia, et al. when we roll out the new WikiTeX. (Thanks to Erik's advocacy.)
Before then, however, it will have met Tim and Brion's stringent security-criteria.
Best, Peter
-- Peter Danenberg . wikisophia.org ..: