<p>I don't think <code>\begin{table}</code> has ever worked on the SE system.  (There is a relevant thread on meta.SE from 2009 here: <a href="https://meta.stackexchange.com/q/16356/187282">Why can't table markup elements be used?</a>)  I don't believe it is supported by Mathjax.  To make a "table" in $\LaTeX$ / Mathjax on the SE sites that support it, use <code>\begin{array}{}... \end{array}</code>.  I have an example here: <a href="https://stats.stackexchange.com/a/63247/7290">DF for regression SS in multiple linear regression when sigma is known</a>, and I discussed the issue on meta.SE here: <a href="https://meta.stackexchange.com/a/192843/187282">Is there any markdown to create tables?</a></p>
