Suggest HN: an off-topic list to filter out popular but off-topic submissions

A set of newsgroups (borland.public.delphi) I have long frequented implemented a mechanism to deal with off-topic conversation a long time ago: there's a separate off-topic newsgroup, and threads that go off-topic are migrated to it by moderators.

I think this idea could help reduce the chaff here in HN. If an article has enough upvotes not to be killed automatically by flags, perhaps it could be automatically migrated to an off-topic / contentious list instead, if it acquires a certain number / proportion of flags?