If someone is banned, is there any way for them to get unbanned?
Yes, contact one of the Admins and convince them to 'unban" them.
Has anyone ever been unbanned?
Yes, recently our friend rjung got banned due to a miscommunication between some of our Moderators, and was shortly unbanned. There are also older examples of posters who were banned for confirmed reasons and who subsequently had their posting privileges reinstated.
Yes. A couple bannings were reconsidered after some grovelling, or merely as new information came to light. I, for example, was once banned when some troll pretended to be my sock puppet. Most of the time I spent banned was due to sleeping in (as I recall, it was the day after classes ended, and a couple days before finals), with only ten minutes involved in clearing the situation up with the administration.
There are some situations where the administration has decided that a banning will be permanent. For example, if you make threats against the board, no amount of begging and pleading will get you back in. And that jackass who kept registering with other users’ names (before they patched that leak) will probably never be allowed back, under any circumstances.
The most recent example of an unbanning would probably be rjung, where the administration decided that they were a bit harsh, and really only should have given a warning.
Now that this question has been answered, I will close the thread, because questions about bannings have a strange fascination for “problem children”.