Max Nikulin <manikulin@gmail.com> writes:

>> 3. Remove verbatim in ("=" org-verbatim verbatim), ("~" org-code
>>     verbatim), and the :type spec.  AFAIU, they are unused. But can you
>>     please double-check?
>
> It seems, before the following commit, verbatim was used to suppress 
> flyspell, but now "~" and "=" are hardcoded.
>
> 9fb2e047d 2016-12-08 09:44:26 +0100 Nicolas Goaziou: Split `org-emph-re' 
> and `org-verbatim-re'
>
> I think, verbatim option should not be removed from `defcustom' :type 
> just now. For some users it might cause fallback to raw lisp value in 
> easy customization UI. Perhaps another warning should be added to the 
> `org-set-emphasis-alist' validator and the option should be labeled as 
> unused in the :type definition.

Makes sense.
What about the attached patch?
The idea is to tag the constant as deprecated.