Stealth mode immunity
I did a little PvP and got killed a couple of times. One time was right next to my home town, so i was able to get back to my corpse while the other player was still looting it.
I went into stealth mode with Shadow Walk and they tried attacking me, but couldn't deal any damage at all, despite being red named. I didn't have PvP on, because of the stupid city auto disable and no auto-enable when you leave a town... but they were red named, so it shouldn't have mattered. I was immortal to them. Also, while i was within 6 meters of them, there was no potential for detection either. It was as if i suddenly didn't exist for them at all.