We used to have Mathjax in the very first days of TeX.sx, but not anymore. See this discussion and also the first answer to this question for some rationale. I'm almost sure there have been other discussions previously, but wasn't able to find them currently.
In a nutshell -- there's no real benefit of having TeX rendering here. Discussions on TeX.sx are mostly focused on the actual source code or a minimal working example that produce the (un)desired result, and for this reason, inline rendering is not only unnecessary, it is actively harmful (when, for example, one would want to quote a command instead of show its result). I'm not even going to mention the implications this has on page loading speed -- try it on a slow machine with older browser on one of the more notation-heavy questions.
Contrast this with Physics.sx and Math.sx (and also Math Overflow) where the notation is absolutely critical to facilitating the discussion. Here on TeX.sx, the plain old source code is sufficient -- questions on aesthetics (although acceptable here) are much less frequent than those from the "where's the problem in this code" or "how do I do X" variety. If need be (or for the sake of saving time to others), the poster should upload an image or even a compiled document if the result is unexpected or non-reproducible by the others, but this happens far less often than you would think.