I just think that the peaceful/battle mode should be changed. There is a little icon next to the Stats GUI, that has two swords straight up if your peaceful, and crossed if your on battle mode. (Diablo fanatics know what i'm talking about
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Now, remember the little symbols that float above your head when your in kingdom mode? When your peaceful, the two swords dangle above your head, pretty small and the same style as the kingdom icons. When your in battle mode... well, you understand now right?
Now, when you click battle mode, and your in it, you can switch right back out again, with a click of the buttion at the top of the screen. Simple. However, there is one catch. If someone is attacking you, you cannot switch out. You must wait atleast 10 seconds (or whatever) after the last damage dealed is done, until you can click the buttion to go into peaceful.
This is going to make people angry when you go: "Awhaha PKer, you can't get me now!", but it will work to keep you from being harassed while leveling up.