Which NPC in WoW are safe to pass nearby?
Playing for Horde I was accidentally killed many time by Alliance NPC, when I happen to come near Alliance city. Usually it is immediate death, so I started to be afraid of NPC, which have "red" name and has a skull instead of level.
But then during quests I noted NPCs, which are also red and skulled, but they didn't touched me. Last one I met right in a neutral city – Dalaran, it was near a guy, which gave me a quest, so I must come close to this skull.. and it didn't touched me.
So is there a reliable way to understand when NPC will kill you and when they will ignore you?
P.S. I add a sample picture of red mob, which doesn't attack from a beach of Isle of Giants (NPC named Beeble Sockwrench) (this is not city area):