Make it so that whenever a player teleports or walks into wilderness that a pop up display message let's the player know they can be killed and might lose their stuff. A lot of players don't seem to know this and love to sound off the global wambulance.

Another idea is to create an area JUST for pkers, possibly called the forest or the jungle, where players can kill each other. That way skillers can stay in wilderness and get the xp and easy farming without having to worry about dying