I'm sorry to hear that. Not having posted on the Straight Dope Message Boards, I can't speak to their level of forgiveness, but I know that
T'Bonz (the admin here) gives serious consideration to readmitting long term posters here who have been permabanned, as long as it's for an accumulation of warnings for relatively run-of-the-mill problems over time rather than a predilection towards obvious bad stuff like fill in the blank ___ist/___phobic posts, making threats, or spamming porn or some such.
The general rule of thumb is to take a few months away or more from the board to allow things to calm down and to float off her radar before asking politely via email if you can get a second chance if you promise to correct your behavior. If you're a long term contributing member, she's usually pretty accommodating. I would hope that the admins over there would be similar if you're a levelheaded guy who just got into some trouble.
That being said, while I understand that a board can be a release valve for dealing with your deppression, and that you come to view it as a circle of friends, please don't let your absence from this one board affect you so much. Look at it as an opportunity to make friends elsewhere or to take up a new hobby or do anything else you might enjoy. Losing the ability to post at a favorite forum sucks, but don't let it get you down.
Anyway, I wish you the best of luck, whatever happens.
