All too often you see "reported" being typed into the general chat or trade channel. The subject that caused the report is usually innocuous, most likely a dispute over what an item is worth or what a player could actually accomplish in PvP. People with short tempers turn this harmless circumstances into debates, which in itself is still harmless; however, the trouble happens when the other side of the debate does not know how to argue properly and takes offense to the situation. They then feel compelled to tattle, which is necessary if it was possible for people to fight their own battles in game. A mutually agreed upon duel is a nice start, but usually the person running their mouth does not have the power to back it up and will not agree to fight back. This is why you should be able to force a fight to happen, it gives consequences to those we misbehave even if they cowardly evade whats coming to them. If trolls get beat-up enough in game, they might start treating people properly, especially when they lose gold because of it.
If PK was allowed, the potential tattler or delinquent debt holder would simply get what he/she deserves: An a$$ kicking and a loss of money instead of a lengthy, reported grievance. Not only would this policy reduce the burden of the report system, it would deter people from scamming and running their mouths.