Infraction: 3. All discussion should be both polite and civil.
Message to User:
You could also shut the fuck up instead of being a smarmy - and worse, incorrect - asshole.
You could, for example, kick the player. He would then, for example, log in and realise that he stands on the graveyard for that instance.
(The Vent issue doesn't really solve the problem of them being offline in the boss room... what are they gonna do? Wait until the fight gets started and log in with unknown amounts of health/buffs/whatever in potential a very bad spot? That isn't tons better if you're talking about a very difficult progression encounter.)
That solution took me about 0.7s to come up with, so it is probably not the best one.