>> Do you mean that the users might want to shoot themselves in the foot
>> and remove '(category . comint)' from the default value of
>> display-comint-buffer-action?
>
> Yes, that's the scenario that bothers me.  Users could do that without
> understanding the subtleties of the issue.
>
>> Then indeed we need to move '(category . comint)' directly
>> to every display-buffer call that currently uses
>> display-comint-buffer-action.
>
> I think we should do that for Emacs 31, yes.

Ok, here is the patch for Emacs 31: