The mods must use a search facility so they can find out how many times posts have been deleted, for example, by poster name. The system will also retain the personal details of previously banned posters, correspondence with them by email, and possibly the details within deleted posts, so they know exactly what was said. I imagine it’s fairly basic though, I doubt there is an AI system to make decisions based on an algorithm, it will be the mods themselves reading the evidence the check turns up, and making a decision as to action based on that. These are only my thoughts, though, others may know more than I’ve surmised.