My account of well over a year and 11k karma was banned by admins presumably for an admin-deleted comment where I said "Hi kids, buy our product!" as a Steve-Buschemi-meme reference, and was flagged as spam. To your point they also have their Comment Quality Score (CQS) which lowers you automatically if you use Proton email aliases, lowers you if you use VPN to access the site, among other things.
Made several polite appeals and requests for clarification, all which went unanswered.
I was banned from subreddits for belonging to r/conservative. Mods wanted me to disavow that subreddit to atone for the sin of belonging to that subreddit.