Some vertical marks won't work in MathJax.
27 Mar 2022I had something like a | b that I wanted to use in MathJax. Usual latex will allow you to use |, but in my case, Markdown was interpreting the | as a table division when also using equation numbering.
Example of the failure:
| $$a | b$ \label{first eq}$ |
The workaround is easy – substitute in \vert for | and it works
$$a \vert b \label{secondeq}$$ produces:
\(a \vert b \label{second eq}\).