Tad, I don't even think that what you saw was her passing for normal. Think about it. Isn't "normal" a loving wife who doesn't want a divorce? What you saw was the same divorce-seeking woman who just had her temper under control for a bit. That's all.
I think you have a tendency to romanticize or idealize interactions with her, in that if she is simply cordial and makes basic small talk, that it is so different from the times that she's spewing, that you suddenly see her as showing some desire NOT to go through with the divorce and, by extension, this must mean she's leaning towards coming back. It's such a leap for you to make, but you make it every time--suddenly she looks good to you again, and suddenly you're wanting to talk about your relationship with her, and really, you don't have a relationship much at all right now.
I guess what I'm trying to say is that I watched my XH go from mean to even kind, but he followed through with every bit of the divorce. Just because they learn to play nice sometimes doesn't mean they are ready to talk about the relationship or showing any sign of coming back. She has so much to go through and to learn before she can ever be an equal partner in a relationship with you.
M45 Bomb 6/09; EA 6/10; Divorced 1/11 Proud single mom of 7 little feline girls and one little feline boy "Fall down 53 times. Get up 54." -- Zen saying