On the topic of Tbird mangling patches (in twisti's entry), Bryan Clark made an extension to expose the knobs in the UI, Asalted:

http://hg.mozilla.org/users/clarkbw_gnome.org/asalted-patches/

Also, contrary to twisti's assertion, the mangling was very much intentional. The flamewar between programmers and those in Mozilla who think that programmers are not a relevant userbase for MUAs was... educational.