I don't really have a dog in this fight, but:

> People who get banned can either start again with a new account or can write a short email showing understanding of why they got banned and asking to be unbanned.

The issue people are bringing up is, what happens when the banee doesn't know why they got banned (not to mention that they got banned)?

For what it's worth, I usually point out Metafilter as a site that seem to do moderation pretty well. There are of course a number of important differences in the way the sites work, but I bet there are a great many lessons that could be shared in both directions.