I've enjoyed doubling up a few times, though mostly with highly different characters. Damian and Darkwind saw highly different sides of Abington, for instance, and it was fun having Arlian in Arcaea where he didn't have to do anything other than his particular thing and RP.
I tend to think it's good for the game to have realms where power is more centralized. If nothing else, people not in power there decide that it's better to help another realm instead, either by joining (yay, more estates!) or passing information (that's pretty much the origin of all of Jenred's somewhat infamous knowledge of events in other realms, by the way, though later there were other reasons).
