The Hot Questions list sometimes includes topics from TeX and mathematics sites. These sites have MathJax enabled to permit users to better ask questions. When a question with such markup in the title appeared in the MultiCollider SuperDropdown on a non-MathJax site, the MathJax markup appeared instead. This was intended and couldn't easily be changed. It probably wasn't a big deal because you'd have to go looking for the Hot Questions in the first place, and users who would do that most likely wouldn't mind.
Now that the new top bar has moved the Hot Questions list from the MultiCollider SuperDropdown to the sidebar, however, it's more of a broken window:
Obviously MathJax support on all sites isn't something that will happen anytime soon, and with reason. But. . . this really does look bad, and it's more visible now that the Hot Questions list is Right There on the Home Page. Is it possible to suppress Hot Questions containing MathJax markup on non-MathJax sites, or otherwise prevent raw markup from invading the front page? (As in a suggestion by Arjan from 2011. Also see other related discussion from 2011.)
No, I'm perfectly aware that it matters about as much as reputation does. Given that it's been nearly three years since this was first discussed, it's possible there's a better way to make it work than enabling markup support on all sites.