gnus-cite indented citation highlighting

[Peter S Galbraith]

Hi,

gnu-emacs-help might be the wrong list to ask this, so please point me
in the right direction if that's the case.

I don't use gnus myself and was told that it does fancy highlighting of
indented citations, using different faces for each level of indentation.
I want to recycle that code for mh-e.

I looked at gnus-cite.el and found that all the work is done by the
function gnus-article-highlight-citation.  Interestingly, it does not
use font-lock, but rather sets overlays.

My initial take on how to accomplish this was to use font-lock using
functions instead of regexps, and determining the regexp when initially
entering a buffer.  That way the fontification could also be done
dynamically when composing a reply.  So I'm wondering if there's a
rationale for the gnus implementation?  Is there a reason font-lock
wasn't used to implement this functionality?

Thanks,
Peter