My question, however, remained unanswered. Until today, the AK did not have the authority to ban for insults (at least according to what was described in the first post).
You must have been looking in the wrong place.
Here is a quote from the previous version of the Blacklist: "(unjustified arguments, rudeness, both on the forum and in private communication)".
If points had been assigned to him by one of the moderators, I would understand why he was banned.