Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> I will try to think of another approach which is more similar to how
>> completion-table-with-quoting does things, but it will be more
>> complicated.
>
> I thought all that's missing is to double the $$ in the text we append
> during completion.

Yes, actually you're right, that turns out to be relatively simple.  And
now the quoting behavior doesn't change at all.  Updated patch attached.

The $ doubling also needs to happen in all-completions, not just
try-completion.  But, with sufficiently robust logic for figuring out
the completion boundaries, that's straightforward: just double the $ in
the newly added text.