Good to hear. I think in all cases it should be left to the coder to
temporarily lift restrictions, even if those are "locked", maybe
with strong warnings in documentation. Speed should always
come a second priority to functionality. Besides, Logview (one
example of what would suffer if widening is impossible) is very
fast.
As an example of why widening might be needed: fontification
may depend on preceding text in the buffer. Maybe standard
Emacs fontification code handles that separately, but e.g.
Logview (almost) completely replaces the standard code here
with a home-grown solution aimed specifically at log files. And
actually this was done exactly for speed.
Anyway, I hope this is finished soon.
Paul