[williamstein]

There's currently around 100 LaTeX functions listed as "Not supported" in the Katex docs at https://katex.org/docs/support_table.html I've been trying hard for a while with my site (https://cocalc.com) to use only katex, but that's definitely never going to happen. Users frequently hit missing functionality, e.g., they have lots of notebooks that use "\mbox", so it's critical to support full mathjax. I currently do this by attempting to use katex, then falling back to mathjax if it fails. That said, as you point out, mathjax has massively improved over the last few years with mathjax3! Thanks for pointing out the quality issues, which I hadn't thought about.