by Gums » Wed Jan 18, 2012 12:55 pm
There is an in-combat indicator that appears either side of your level when you engage NPCs. This looks like a sword and shield on a gold background. The PVP-enabled indicator is the red flag with crossed swords, exactly the same as the toggle button in the top left.
If it's definitely the PVP-flag thats popping up whenever you attack things that aren't other hostile players, then that would seem to be a bug! If you do ever find yourself apparently PVP-enabled, and the button in the top left is active, you should be able to toggle yourself off.
PVP is currently a work-in-progress, we plan to add a lot more structure to it in order to make it less trouble and more fun!