Unfortunately, some users complain about the approximation. OTOH, I'm
pretty sure that most LaTeX users can parse sub/superscript LaTeX code
without any fontification at all.
If there is no easy way to fix it, I may prefer to disable this fontification,
because it displays something which is wrong (also the superscript is too small in my opinion,
sometimes the character is unreadable).
The current \(a^nb^n\) is actually displayed as \(a^{nbn}\) which is misleading.
This is what bothered me first.
OTOH, I have set up preview of formulas (actually I did it for tikz diagrams) and it works well.
It is slower, and I use it for complicated formulas only, but at least it is exact.