It was an unfortunate bug in the software.
What it was supposed to do was to detect when a recent posting had swung somebody's trust ranking down into the negative numbers, and delete the post and send them a message along with banning them.
What it did do was detect when someone had posted any message at all, delete that person's comment, and send a totally different random person a message saying they had been banned. I am not good with computer, apparently. I made a test suite but the bug was of a nature that snuck past the test suite. It only happened once before I disabled the offending functionality, with you as the random message recipient and Midnight@slrpnk.net as the random comment deletion victim. I posted about it and had already disabled the malfunctioning stuff, but I didn't realize that the random message recipient victim was different from the random comment deletion victim.
Sorry about the breakage. I'll fix it.