Dollar signs are common LaTeX delimiters. It's probably something in the underlying MathJax renderer. You might have to escape them if you intend to double up on dollar signs regularly.
From 3.0 the addon uses KaTeX math renderer instead of MathJax (because KaTeX is faster and causes less problems). If you want to stay with MathJax — do not update!
Features
New math renderer — KaTeX
Reduced the size of addon (less files)
Works faster
Long equations are automatically break into few lines (yep, no more horizontal scrollbars)
In the previous versions, you can write latex fomular using that bbcode. Now it doesn't work anymore and only work with \( \) and \[ \].
I may not remember correctly since I used that years ago. Just checking.
Yeah I forgot about XF smilies. I think the only solution here would be creating a custom bbcodes [math] (for display math) and [imath] (for inline) and disabling smilie rendering inside:
I will make a patch soon that adds these two bbcodes.
Added a two bbcodes for math rendering: math for block math and imath for inline math.
Smilies and other bbcodes are not rendering withing these two tags.