I got permabanned from /r/canadapolitics because I explained to someone why I thought their comment was being downvoted. No warning, no appeal. They have a rule there that prohibits downvoting even though there's no way to stop it or detect who's doing it, and apparently my comment was enough for the mods there to go "aha, a downvoter!"
Nothing remotely to do with Nazis, but not a safe forum nevertheless.