Hello!
It seems like sitting in stairs doesn't really work in multiplayer... it shows you're sit for the client, but not for others! (they still stand next to the sit).
One more thing is that, once in a chair, if going into another one and sometimes leaving it, the game still considers that you're in and you have to relog to do any action (can't drop blocks, or place, etc).
Thank you for your awesome mod =p!

having this same issue in quark 200