So I've been camping Cinder for quite some time. I've also been using the custom group finder to phase to different realms and kill their spawns. I've noticed that any time I phase into a PvE realm, and back into my PvP realm, I am no longer flagged. During this time, I am unable to hit anyone flagged for PvP or anyone with the blood coin debuff that allows them to hit whatever. And conversely, they are completely unable to hit me.
Pretty nice considering I go AFK all the time. I've mainly only been using this for camping the rarespawns, so I'm not sure how far you can go before becoming flagged again. I imagine changing zones will undo this. Hitting mobs, however, will not flag you.
So, steps in order:
Open up the group finder.
Find a PvE server and get accepted into a group, and phase into it.
Leave group, and phase back to your realm.
Enjoy being immune to all the douchebags.
Sorry if this is a repost, I'm just back to the game in time for the new xpac.