bug#25309: 11.89.8; multi-level script fontification stacks incorrectly

[Uwe Brauer]

   > Uwe Brauer <address@hidden> writes:
   > Hi Uwe,


   > Yes, exactly.


   > Sorry, but I think there's no value in a feature which only works in the
   > simplest cases and might be wrong otherwise.  Have a look at Gennady's
   > screenshots.


I have seen his shots, these are border line cases, which are used very
little. Look I have written mathematics with latex over the last 25
years and in countless occasions I have used ^or   but never nested
expressions and this is also true for the publications and writings I
have seen in these years. I reckon that 95 % of the people writing
mathematics never use nested ^. So I could understand your argument if
there were 50 % non nested and 50 % nested but it is the case. Please
don't move us back to the middle age.

   > There are examples where its completely confusing with
   > `multi-level' and would definitely make you read something else than
   > what has been written with `invisible'.

What's about the following compromise:

Remove multi-level, but leave invisible and add to the docstring
something like

Please note that invisible only works for a simple sub and superscripts.
Nested constructions are not supported, in fact those can be displayed in
a confusing way. If you need those constructs please do not use the
invisible option.