Artaxerxes
Look out, he's got a gnu!
I would put a soft border about 3/4 of the way through the first thread, and then a partial hard border between the two threads, and then allow posting on the first thread only for posters who had already posted on the second thread at that point in history. For posters who only posted before the soft border through the first thread was implemented, they would be allowed to post on the second thread if 50% of posters from after the soft border agreed, although they would have the right to post emoticons only, in any location. For posters who could prove that a grandparent had, or would have, posted on the second thread but only before the soft border was imposed on the first thread, they would be allowed to post on either thread but not move any arguments from the second thread to either portion of the first thread, unless their grandparents had, or would have, only ever posted on the first thread but prior to the hard border having been agreed in the preliminary agreement that will by the way have to be negotiated, before any of the new borders are implemented. Both threads need a parking area for any posters awaiting confirmation of any details of the rules which may not have been clarified prior to the changes taking place.
Will you allow 90 day visas for musicians to post in either thread but have to wait 180 days between posts?