Weapon/tool durability decreases when hitting playing in no-pvp mode. (SMP)

This one is pretty straight forward. On a vanilla server with PVP mode off, weapon (and tool) durability seems to decrease when hitting a player. This can be pretty annoying in combat when accidentally hitting the player in no-PVP still eats durability.

Tested with a wooden sword, after rapidly clicking the sword was destroyed within a minute.