> If no one has a better idea for a simpler implementation,
> then this patch fixes the problem by skipping the sentences
> that already have two spaces at the end:

The filter will also allow redefining it with own logic
such as skipping known abbreviations that don't require
two spaces, i.e., e.g.:

  (defun repunctuate-sentences-filter (_start _end)
    (not (or (length= (match-string 4) 2)
             (looking-back (rx (or "i.e." "e.g.") " ") 5))))