OK, clearly @eviltrout has this in hand, so I’ll leave this alone for now (contact me if I can help). Hopefully my comments at Email subject configuration options and/or my pull request code with adding the “Re:” are useful.
I would add to please include with the configurable subject lines the option to include the “Re:” in replies, which I am pretty sure is part of the requirement for Mail.app to thread properly (stupid though that may be).
Also, with the addition of a List-Id header, there is no real necessity for the [Site Title] in the subject line, which makes the option of just using a subject with just the [category] much more appealing.
Thanks!