This hint showed how we could add a set of Apply/Cancel/OK buttons to Mail.app dialog windows. It looked innocent enough, but broke the signatures as described above. I don't know whether this only happened with the latest upgrade or before.
[robg adds: It seems this hack also affects the ability to add new accounts, and potentially other changes in the Preferences section. I have added a warning at the beginning of the previous hint, but thought it worth mentioning this as a standalone hint in case anyone else is having odd Mail preferences issues. I had the hack installed on my machine, but hadn't noticed the problem until I was testing this fix -- and the Prefs are definitely broken with the previous hint active! Thanks to ars for finding this subtle breakage, and apologies for the original hint -- a good example of some of the risks one takes when playing around with the behind-the-scenes workings of the OS. Have you backed up lately? :)]

