bug#5971: 23.1.95; `delete' modifies default value instead of buffer-local value

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

Visit this file, without loading it:
http://www.emacswiki.org/emacs/wide-n.el
 
Change this line:
(setq wide-n-restrictions
      (remove (cons mrk1 mrk2) wide-n-restrictions))
 
To this:
(setq wide-n-restrictions
      (delete (cons mrk1 mrk2) wide-n-restrictions))
 
Then load the file (with `delete'). Then:
 
In some buffer X, do `C-x n n', then `C-x n x'.
Check the value of variable `wide-n-restrictions'.
 
In another buffer Y, just check the value of the variable. You will see
that the default value, which should be `(all)', has been changed to be what the
new value is for buffer X.
 
Try the same thing again (starting from scratch), but using `remove' (the
original code) instead of `delete'. There is no problem now: only the
buffer-local value is ever set.

This doesn't seem right to me.
 
In GNU Emacs 23.1.95.1 (i386-mingw-nt5.1.2600)
 of 2010-04-03 on G41R2F1
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags
-Ic:/imagesupport/include'