Hi again,

Folding $x \in [0,1]$ doesn't work as intended: [0,1] gets folded as if it
were an optional argument to \in.

The issue is that, when called on 'math macros, TeX-fold-item-end calls
TeX-find-macro, which skips past any {...} or [...].

The attached patch makes an expection in TeX-fold-item-end for 'math
macros, so that only the macro name itself (e.g., "\in") is folded.

This only affects the folding of macros in the list
TeX-fold-math-spec-list-internal, and looking through that list, I
didn't spot any for which this change would have an undesired effect.

Any feedback welcome.

Thanks, best,

Paul