Max Nikulin <manikulin@gmail.com> writes:

> On 21/11/2021 17:01, Ihor Radchenko wrote:
>> Max Nikulin writes:
>> 
>>> My draft version is attached. Ihor, thank you for inspiration. Feel free
>>> to improve it. I hope, it makes problem more apparent to user who tries
>>> to customize markers.
>
> A patch is attached. I have dropped changes in documentation since I am 
> not the author of them.

Sorry for the late reply.

I have reviewed the patch, and I'd like to suggest a new version with the
following changes:
1. Use `set-default-toplevel-value' instead of `set' that might be
   quirky in some scenarios.
2. Use `warn' instead of `message' as more alarming.
3. Remove verbatim in ("=" org-verbatim verbatim), ("~" org-code
   verbatim), and the :type spec.  AFAIU, they are unused. But can you
   please double-check?