Think half the time that issue happens, when someone invites you and then like a few minutes later they say sorry is becuase either their "d/c'd" person has come back. Honestly if you invite someone though and your other person decided to come back and they have been offline for a certain amount of time, their loss and shouldn't have to deny the person you just invited to party. Its rude and some people spends hrs lfp and that just ticks them off even more.