bug#15917: 24.3.50; manual: mention keys reserved for users

[Drew Adams <drew.adams@oracle.com>]

> >> How about "should not conflict"?  Otherwise, please propose an
> >> alternative.
> >
> > Better, yes.  But that could mean that we expect that,
> > most of the time, they won't (automatically).
> 
> I don't understand the second sentence.  Could you please elaborate?

"Should" has at least two meanings: (1) you should
do something (like must but less strong) and (2)
something probably will happen.

#2 says that we expect that something will likely
happen, but it doesn't say who makes it happen.
It's passive.  There's no telling someone that
you want them to do something.  It's just saying
that something will likely happen (somehow).

My suggestion is that we not allow such a reading.
Remove such ambiguity.

> > Active voice here removes such ambiguity, I think.
> >
> >   Key sequences that consist of @kbd{C-c} followed by a
> >   letter are reserved for users.  Please do not write
> >   code to be used by others that binds these keys.
> 
> Such advice is already in the elisp manual.  The user manual should
> rather advice users which keys are reserved for their use in their Init
> file.  So I don't think writing about "code to be used for others" is
> suitable here.

Sorry, I thought this was for the Elisp manual, node
`Coding Conventions'.

If this is for the user manual, and it's only a message
for users for their own use of keys, and not also users
who provide default key bindings for others (e.g. in
code they write), then my suggestion is to remove any
such text, beyond saying that these keys are reserved
for personal use (not just "users").

If you want to add (for some reason) that users can at
least expect that code Emacs distributes won't bind
such keys, that's OK too.