RE: Eliminating "changed in Emacs outside of Customize"

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

    I believe that you were confusing with the defcustom form, which does
    not override an already set value (_unless_ the :set function does so)
    and its default :initialize function `custom-initialize-reset', which
    nevertheless executes the :set function _even_ if the value is already
    set. ...

Interesting. I wasn't aware of these keyword args to defcustom.

Something I discovered recently that is perhaps related (perhaps not), and
I'm not sure is documented: subsequent defcustom's redefine the `standard'
value of the variable (that is, the value that you can reset to with Reset
to Standard). The current value is not changed; only the `standard' value is
changed.

Of course, it's not recommended for multiple libraries to use defcustom's
for the same variable, but if they do, the last one executed wins, in this
respect.