Recently I discovered a user that I talked to a lot was banned for a little over 300 days. It seemed strange, so I looked into it myself. I found this chat message:
You're suspended on Stack Overflow. You should probably not be chatting in SO rooms.
You may consider that a formal warning.
He was warned by a mod he shouldn't talk on Stack Overflow chat because he was suspended on Stack Overflow. If you read a little further, you can see he complies and leaves.
However, he told me (through other means) that that was the reason for the ban. It seems to be a harsh and uncalled ban, since he complied with the warning. I seen no evidence of him talking on Stack Overflow chat after the issue. So, out of curiosity and wanting to correct a possible mistake, why was the user actually banned?