I am user of /polru/. There is a ban evader who keeps posting bait by changing IP (text posts). You already made lock for unknown users, now make so it can use the simple fingerprint of POST request (e.g. DNT header presence, Sec-GPC header presence, user agent string all in combo) so board owners can block their fingerprint if the post count is lower than N posts. Check req_sig in 4chan source code leak and browser_id to see how desuwa operates it on their side.