If somebody invites you to a party, and you're already
in one - it tells the inviter that he's in another party.

Could it be modified that one could jump from party to another without
quitting the first one. Like 'party swap', and it takes the invite and quits
the current party. Or make 'party join' quit the current party and join the
invite. If more than one invite is presented, they are ignored until the
party invite expires.

~/A