Very revealing.  However, that post was written in 2005, and the following
statement is found at the tail end:

The good news

The behaviour of custom due to more than one custom-set-... statement will
be changed in Emacs 21.xx. I've been told that
> Multiple calls to custom-set-variables should work in Emacs 21;
> if you customize, all the variables go into the first one,
> and the rest are deleted.

I can still dream.  I have to say, though, thank you very, very much.  This
certainly clarifies the issue well.

Alan

On Tue, Mar 8, 2011 at 4:33 PM, Suvayu Ali <fatkasuvayu+linux@gmail.com>wrote:

> Hi Alan,
>
> On Tue, 8 Mar 2011 16:13:34 +1000
> "Alan E. Davis" <lngndvs@gmail.com> wrote:
>
> > I have noticed the message from within the customization interface
> > that some variable or another was set outside of customization, and
> > there may be unpredictable results.  Wonder what that really means,
> > though.   It's still a variable, isn't it?
> >
>
> Say you customise the templates outside your custom-set-variables
> block. Now if you use the customise your templates with customize and
> save them, it will be saved in the custom-set-variables block. For the
> current session of emacs you might not experience any problems, but
> when you restart emacs depending on which comes first the setq or the
> custom-set-variables your templates will be set accordingly. It is
> difficult to predict for me which will be the case. For more on this
> you can look here[1].
>
> Hope this helps you understand the issue with what you are attempting.
>
> [1] http://www.dotemacs.de/custbuffer.html
>
> > Alan
>
> --
> Suvayu
>
> Open source is the future. It sets us free.
>