AFAIK, PokerStars is the only site that not only displays when a player is sitting out, but also folds their hands. In certain rare circumstances, the hand may play. I think if the dead hand is in the BB with exactly the amount of one BB remaining, the hand plays if there are no raisers.
I play on 888, PartyPoker, ACR, BetOnline, and Sportsbetting. Only PP doesn't show when a stack is dead money, but auto folds them even to limps. All the others let the dead stacks play if there is no raise, or if they are all in.
I prefer the PS approach. I should think everyone would. The most annoying part of sitters is the change in the table dynamic. That is the only problem that exists across the board.