Well, multiversion dedicated servers have been around for some while now, and TSF users running JJ2+ have been able to join all 1.23 games since the latest update. So it's not a stretch to believe the communities have gotten used to each other, at least to some degree. And since you don't even need 1.23 to play online anymore, only 1.23 users would have to get TSF. The only thing stopping them is either their willingness to search and spend on sites like eBay or their own morals.

Plus this whole desire to keep the "1.23" and "TSF" communities separate has got to stop. What other game deliberately has this?