Too add it to the zones or clan halls or really anywhere besides the public villages seems unnecessary.
That's really the only place RP and OOC conflict. The zones are for fighting, the clan halls are for whatever the clan wants them to be.
In zone four Kamui asked us to stop spamming and we scattered like flies. While OOC can happen there, it's not usually too much. And what would the OOC in the zones be anyways?
In clans, it's up to the clan leaders themselves to decide what should be posted and what shouldn't be, unless what's being posted breaks the rules. You could totally make a "No OOC" clan and just boot anyone who broke the rules.