Am I allowed to loot items dropped from monsters that are not killed by me (after the time buffer) or is this an offense? Am I allowed to loot items dropped by other players, or is this an offense as well? If I'm not allowed to loot items dropped from monsters that are not killed by me (after the time buffer), especially on maps that are full of dropped items and the attackers do not pick them up, then why have the time buffer that allows me to loot afterwards? Why not just let the items disappear without letting other players to loot.
No official rules about looting someone's items. When a player kills a mob, other players can't pick up the drops for a short period. I assume if the player hasn't picked up the drops, you can go ahead and take it for yourself. (Unless certain rules were discussed, such as at a Zpq for example)
