Walls are often used on doors; deletion upon leaving the room would mean the wall disappears if the owner goes through the door and is just a few steps away, perhaps baiting others to come through the door. I believe the 1 hp minimum is fine on its own, as it requires someone to be there to actually kill a player.

Descending from that, putting the check in SomethingLeft wouldn't catch the owner logging off in another room. This periodic check seems the best solution to me.