"Basil L. Contovounesios" <contovob@tcd.ie> writes:

> Eli Zaretskii <eliz@gnu.org> writes:
>
>>> From: Eric Abrahamsen <eric@ericabrahamsen.net>
>>> Date: Sun, 17 Mar 2019 19:59:41 -0700
>>> 
>>> >     So it's a bug.
>>> 
>>> The value of `mail-header-separator' gets added to
>>> `message-font-lock-keywords', which does the actual fontification. Using
>>> setq to change the value of `mail-header-separator' did not change the
>>> font lock keyword, despite setting the variable before message.el is
>>> loaded (or is it pre-loaded?). Using the customize interface to set
>>> `mail-header-separator' *does* work as expected.
>>
>> Right.  So I don't think there's a bug here.
>
> Actually, I think message-font-lock-keywords can do better:

[...]

> This is similar to what mail-font-lock-keywords does in
> lisp/mail/sendmail.el, namely adapt the font lock keywords to changes in
> mail-header-separator.

For reasons explained elsewhere in this thread, I think the current
behaviour is a shortcoming, even if it's not considered a bug.  I would
like to push my patch which addresses this, and which I reattach for
convenience.  WDYT?

Thanks,

-- 
Basil