The wiki previously had <math>...</math> tags render latex code; this no longer works (the tags and the latex code are displayed in plain text instead). Example article with this problem: http://wiki.lesswrong.com/wiki/Conservation_of_expected_evidence

I've been handling this one

Maths markup had issues with 1.18. The wiki has been updated on the 18th of March and I've confirmed that it's working again