From what I understand, players will be able to activate two back up players to log in to their account for maintenance while offline. Coplaying, as was in the original, and account sitting won't be available here like it was in tribal wars. It is against the rules for two players to be playing solely the same account.
I think it adds a great deal more control to the game, actually. Leaders can't become bogged down by inactives, you don't get high activity accounts run by 4 or 5 players exclusively, lording over new and solo players. No more account contesting between co-owners.
It all go towards pacing the game down from what is currently familiar in tribal wars.
There will be a different take on account sitting in this game called coop gameplay, which has yet to be released.