"AFK farming" in For Honor is the practice of keeping your character moving in a match—say, by using a rubber band to hold your control stick forward—while you're off doing something else. It's a way to pick up end-game rewards and progress your character without actually playing the game, and of course it's very much against the rules. Ubisoft said earlier this month that addressing the problem "has become a top priority," and that violators would be hit with anything from warnings to suspensions, either temporary or permanent.
On the off-chance that anyone thought it was a bluff, a message posted recently in the For Honor subreddit made clear that it was not. In it, Ubisoft announced that the first round of warnings about AFK farming was issued last week, and the first wave of bans went out yesterday, leaving roughly 1500 players out of the action for three days. New warnings have also gone out to another 4000 AFK farmers.
"Using a cheat engine to exploit AFK farming is against our Code of Conduct, and these impacted players may get a permaban for cheating," Ubisoft wrote. "In all cases, impacted players will receive an official email detailing their sanction and the reason behind it."
What you won't receive, however, is any information about how Ubisoft determines who is in violation of the rules, or how it came to that decision: Its initial warning about incoming penalties said that "no details about the state of our investigation into this matter will be disclosed at any stage. Rest assured that sanctions will only be applied if there is clear evidence." If you're unsure about the rules, you'd probably be well advised to spend some time with the For Honor code of conduct, and also the sanctions FAQ.