As mentioned on r113203#c31944, currently the menus are always in English.
They need to be in user language.
Version: unspecified
Severity: blocker
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=49267
https://github.com/mathjax/MathJax/issues/493