>>> I propose to refactor such code
>>>
>>>   (message "Ispell error: %s" output)
>>>   (sit-for 5)
>>>
>>> to a new separate function, e.g.
>>>
>>>   (important-message 5 "Ispell error: %s" output)
>>>
>>> with a simple implementation
>>>
>>>   (defun important-message (seconds format-string &rest args)
>>>     (apply #'message format-string args)
>>>     (sit-for seconds))
>>>
>>> Then users could easily override such annoying delay.
>>> Or maybe even the default implementation can check
>>> if set-message-functions already contains set-multi-message
>>> that ensures that the important message will not be missed,
>>> and not to use sit-for in this case.
>>
>> I don't mind much, but is this really the best we can do?
>
> This is just the first thing that we could do.
> So the first task is to find all such places,
> and replace them with the single function call.
>
>> Asking users to customize Emacs by overriding functions is not very
>> friendly, and in this case we certainly could do better, for example
>> by making 5 be a defcustom.
>
> A defcustom would be one option.  'set-important-message' like
> implemented by Ihor would be another option.  All this could be
> added after creating the new function 'important-message'.

So here is the new function 'important-message' and its calls
in two discussed places.

I'm not sure why 'after-find-file' uses non-nil NODISP arg
in (sit-for 1 t).  This means is that the message is not
displayed?  Then why 'message' is called?

I'm asking this because if NODISP is unnecessary then
the signature of 'important-message' without NODISP
will be shorter and more nice to use.