Subject: bug#31042: Emacs 27. Inserting a character doesn't always "deactivate" the mark.

From: Eli Zaretskii <[email-masked]>
Date: Tue, 03 Apr 2018 17:08:00 +0300

> Date: Tue, 3 Apr 2018 13:42:46 +0000
> From: Alan Mackenzie <[email-masked]>
> 
> On a related note, it appears that in the same function, the file
> locking is done for the first change in a buffer.  This locking would
> appear not to be done if that first change to the buffer happens when
> inhibit-modification-hooks is non-nil.  I haven't tested this, but it
> would appear to be part of the same bug.

This is a feature, see the doc string of inhibit-modification-hooks.