Pandoc’s specific markdown has had these for 20 years. They are from latex itself not mathjax.
You’d think the list would have talked him out of it if it was a problem.
What legit use of $ as ‘dollar’ is missed by this spec?
> 8.13.1 Extension: tex_math_dollars
> Anything between two $ characters will be treated as TeX math. The opening $ must have a non-space character immediately to its right, while the closing $ must have a non-space character immediately to its left, and must not be followed immediately by a digit. Thus, $20,000 and $30,000 won’t parse as math. If for some reason you need to enclose text in literal $ characters, backslash-escape them and they won’t be treated as math delimiters.
> 8.13.1 Extension: tex_math_dollars
> Anything between two $ characters will be treated as TeX math. The opening $ must have a non-space character immediately to its right, while the closing $ must have a non-space character immediately to its left, and must not be followed immediately by a digit. Thus, $20,000 and $30,000 won’t parse as math. If for some reason you need to enclose text in literal $ characters, backslash-escape them and they won’t be treated as math delimiters.