#992 added support for e.g. é in both math and text mode, mapping to \acute{e} and \'e respectively. This felt natural to me... but I haven't been able to reproduce this behavior (specifically, the math-mode behavior) in LaTeX. I'm compiling the following with xelatex, and only the text line is rendering:

\documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont{xits-math.otf}
\usepackage{xeCJK}
\begin{document}
é私はバナナです。

$é私はバナナです。$
\end{document}

I may be missing some packages though. If this is really the state of XeLaTeX, should we remove support in KaTeX? Alternatively, we could try to add support via the mythical katex.sty.

Related, I am wondering whether to add support for CJK in math mode, but rendering as text symbols. This is how \ae works in LaTeX (with a warning), but doesn't seem to be how it works with CJK...