It is due to systematic rule breaking even after multiple warnings. If you break the rules of HN you get banned after a while. And if there were sub-HNs here and one would take almost all the moderation time it wouldn't exist for long.
Also, if it is about a board usually called "TD" that one is quarantined, not banned.
Also, if it is about a board usually called "TD" that one is quarantined, not banned.