1. Demon!Dean's speech patterns and inflection are different from Dean's. The tilt of his head, the lilt of his voice, are very Not!Dean. Lighter. Maybe being Not!Dean is lighter than being Dean. All of the responsibility of being Dean Winchester, savior, protector, warrior, martyr; it's all gone. Maybe because he finally gets to do the one thing almost everyone else eventually gets to do, the one thing he hasn't been able to do since he was four years old - stop worrying about monsters - maybe the weight of that being lifted is enough to lighten his load. Or maybe it's something else. Maybe it's not the weight of the monsters he's been carrying, but the people. The people he loves - those who are still with him (temporarily; it's always temporary, he always loses them one way or another) and those he's already lost, who have all thrown themselves onto the hand grenade that is Dean's life, who all died because of something he did or something he didn't do; they're gone but that doesn't mean they weigh any less, but now that they're been excised from his heart, along with his guilt and worry and responsibility, maybe he's so much lighter that even his voice is lighter.
( Maybe... )