RE: bind commands that change buffer contents to `undefined' when read-only?

[Drew Adams]

> > 2. It doesn't really help users see that such keys are, in
> > effect, available for binding in such read-only contexts.
> > That was a main motivation behind my
>
> *All* keys are available for binding.  The only thing that really
> matters in this respect is whether the user uses the predefined
> binding or not. If not, then the key is available, regardless of
> whether the associated command is useless or not.

Of course.

I, for one, am more likely to choose a key binding as "available" if it is
undefined - that's what I meant. But yes, you are strictly correct: all keys
are available for rebinding.

And yes, being bound to command `undefined' is not strictly being undefined
either... But it indicates that the current mode/buffer/map has declared no
a priori use for that key. That's a good indication to a user that s?he will
miss nothing by binding that key. I'd say it's practically an invitation.