The problem with comments seems to have resolved itself. If we used the "show x more comments" link, the MathJax would become unrendered in all comments on that page. However, this is either intermittent or has gone away.
However, when I edit an answer and immediately after I post the MathJax is unrendered:
After posting, the MathJax is rendered when I refresh. The page will appear fine to anyone who is not editing it, but this makes it very hard to edit.
System Details: MacBook Pro (OS X 10.10.4), Firefox 40.0.3 and MacPro (OS X 10.10.5), Firefox 41.0
MathJax Renderer Used: HTML-CSS