On Fri, 12 Apr 2013 22:45:45 -0700 (PDT)
Rand User <rand.user@ymail.com> wrote:

> >>  > This command is obsolete since 24.4; use `C-x 2' instead

> I think explicitly giving the name of the obsolete command
> 
> and the replacement command would be better. Something similar
> to the format used by `define-obsolete-function-alias'
> 
>     `split-window' is an obsolete command (as of 24.4); use `split-window-below' instead
> 
> 
> or maybe
> 
>     The command `split-window' is obsolete (as of 24.4); use `split-window-below' instead
> 

In (info "(elisp) Documentation Tips"):

  Format the documentation string so that it fits in an Emacs window on
  an 80-column screen.  It is a good idea for most lines to be no wider
  than 60 characters.  The first line should not be wider than 67
  characters or it will look bad in the output of `apropos'.

Although I don't find a convention on echo area, I think it is good to
follow this convention.  See the attached files.

> >> Also, `C-x 2' looks more like a key sequence than a command name.
> >
> > Yes.  There are 2 reasons to use `C-x 2' here:
> >
> > 1. It is usually too long to display two command names in the echo area;
> > (I even want to drop the " since 24.4".)
> >
> > 2. It is more convenient for users to execute the command, since they
> 
> Encountering obsolete commands should be pretty rare,
> 
> so I think a detailed message is more important than
> the convenience aspect.

The detailed message can be in the output of `describe-function' and
`describe-key', the message in echo area shouldn't be too long.

> Perhaps something like `disable-command' could be used
> instead of just a message.

Sounds fine to me.

-- 
Xue Fuqiao
http://www.gnu.org/software/emacs/