Richard Stallman <rms@gnu.org> writes:

For what it's worth, I have C-x u undo-only C-x C-u undo-redo > [[[ To any NSA and FBI agents reading my email: please consider    ]]]
> [[[ whether defending the US Constitution against all enemies,     ]]]
> [[[ foreign or domestic, requires you to follow Snowden's example. ]]]
>
> There are two problems with C-?:
>
> * It requires two shift keys, so it is inconvenient.
> (The bindings for undo ensure it can be typed with just one
> shift key on all usual terminals.)
>
> * It does not exist at all on ttys.  (I don't know whether we can
> change that on Linux consoles.)
>
> Whether constitutes a problem for the undo-redo feature depends on the
> precise meanings of the two commands.  I don't know those details
> so I can't judge.
>
> M-_ is likewise inconvenient because of the need for two shift keys.
>
> Defining these keys in addition to the existing binding for 'undo'
> can't do direct harm.  But it may disappoint the users you're trying
> to help.

-- 
♈ Id: kg:/m/0285kf1  🦮