I *think* I've fixed MathJax on mathstodon.xyz. For some reason it wasn't using the latest JS files, so I deleted the public/packs dir and recompiled.
I also took the opportunity to use the CommonHTML renderer by default and turn off typesetting on startup, so it might be slightly improved in some ways.
@christianp hm... Still getting 2.7.0 at https://mathstodon.xyz/@christianp/99099969969750514 (I'm on the tusky app anyway so I'd totally want SVG server-side 😉)