While searching for degrees of field extensions, I discovered that the Latex is not being rendered properly for this question, but only in the search. When I visit the question, the box isn't there; it renders properly.
I made sure to research it, to ensure that it wasn't just like the temporary failure to render I get when I ask questions that make heavy use of \def. But the problem persists.
I tested it out in both Chrome and Internet Explorer; both have the same problem.
Search previews are created without much, if any, attention given to LaTeX syntax. For example, a preview can end in a middle of a formula, resulting in unrendered code which can also interfere with the code of subsequent search results.
But this issue is different, because the entire formula is present in the preview. Search previews are sanitized by replacing < with HTML entity < (actually, it's spelled < in this case, which is odd but makes no practical difference). Of course, HTML is not valid TeX. But this particular entity is in fact supported by MathJax, precisely because it often replaces the < character.
So... Why does not $a < b$ render here? No answer was given in that thread, either.
