bug#70587: More buffers that ought to be read-only

[Dan Jacobson]

EZ> I asked for a complete reproduction recipe, so could you please
EZ> provide such a recipe?

$ emacs -Q /etc
then on e.g., adduser.conf.update-old, press "=", and enter the second
name. Redo shows I did
(dired-diff "/etc/adduser.conf" nil)

Also *Shell Command Output* should be in View mode.
Otherwise every time we expect to scroll it,
the strangest thing happens. We end up inserting a
space (' ') into the beginning of the first line.
And, a half an hour later, having forgot that mishap,
end up sticking a "q" in it when it's time to leave.
q as in quicksand, which is what the buffer feels like.