Typing
`\$`
on a MathJax-enabled site renders
\\\$
instead of the expected
\$
On the preview, the rendering is also wrong, but it only renders \\$
, as can be seen in the following screenshot:
This happens also on Math Meta, and breaks item 15 of their very popular MathJax tutorial.
This recent bug report might also be caused by this, although what I report here is not limited to Crypto.SE.
$$
(but apparently not those starting and ending with$
); see this closed question.