Use a different key from `C-M-c' for exit-recursive-edit?

[Drew Adams]

For consideration after the release -

`C-M-c' is bound to `exit-recursive-edit', and that's been the case for
decades. I don't see any good reason for this binding, other than legacy. I
think it would be better to bind `exit-recursive-edit' to something else.

One possibility might be `C-}', which is similar to `C-]' for
`abort-recursive-edit' (same key, shifted, on many keyboards; and also a
closure bracket char). I don't have a strong opinion about which key is
used, however, other than `C-M-c'.

The reason I'd prefer not to use `C-M-c' for `exit-recursive-edit' is so
that users or libraries might use `C-M-c' as a prefix similar to `C-c'. For
mnemonic purposes, it could be useful to have parallel (analogous) bindings
on prefixes `C-c' and `C-M-c'. For example, `C-c a' and `C-M-c a' might have
analogous uses, and likewise `C-c b' and `C-M-c b', and so on.

I'm not sure I'd go so far as to propose reserving `C-M-c' for users, the
way that `C-c' is reserved, but not binding `C-M-c' by default would at
least leave more possibilities open.

WDOT?