Imagine this scenario: You play on a non-RP PvE or PvP server. You come across a quest such as The Art of Persuasion that brings out some sort of reaction in you. A while later, you're leveling a different character and come across the same quest. Is your reaction the same, or does the toon you're playing affect your reaction? Do you react at all?
For me, my character colors my reactions to the quest. The Art of Persuasion made me cringe on my druid, hunter and paladin, but I absolutely reveled in it on my warlock and death knight. The Nesingwary quests, D.E.H.T.A. quests, and even whole zones can make me elated or squirm. Now that Cataclysm has hit, it has only gotten worse. I could barely stay in my seat questing in Hyjal, I was so involved in the quests. I made snarky comments in /say to NPCs, I refused some quests I found distasteful, and I reacted like I think my druid would have to the events around me. Even at the end, after the final quest, I felt like I have many times at the end of a large campaign in a traditional tabletop RPG: I felt accomplished. My character had done something.
Granted, I come from a long background of roleplaying. From tabletop games to LARPs, I've played one character or another for over a decade, so it's second nature to create and act out a new persona. I don't play on an RP realm because I generally don't agree with where many WoW RPers take things, but I do enjoy getting to know my character as more than just my avatar in Azeroth. No matter how hard I try to keep him quiet, my character will eventually get a few words in.
Does RP get into your gaming, no matter what? Can you withstand a character's call to live and not just be?