As seen in the recent sandbox question, TeX markdown isn't enabled on Meta.
It should be. It's needed for the sandbox, and we're likely to have questions on how to do something in TeX, TeX bug reports, TeX feature requests, and, after the feature is more familiar, questions which assume that TeX is enabled on Meta and try to use it.
I don't want to have to go over to Math.SE and try stuff on their meta (they have it enabled). I don't think they'd like that much... :)