Re: C-u prefix input (e.g., C-x f / set-fill-column)

[Juri Linkov]

>> So the point is that plain "C-x f" should produce an error because it
>> is too similar to "C-x C-f". No default, and no further query.
>
> I think a further query would be appropriate. It is non-destructive,  easy
> to abort, and conveys the same message via the prompt.

Maybe this is for newbies who don't know how to abort this prompt
with C-g?

> (It's too late to choose a different binding!)

Late or not, a good and easy to remember key binding would be `C-x M-q'.

-- 
Juri Linkov
http://www.jurta.org/emacs/