Honestly? I feel like it doesn't matter if you say thanks, you don't, you shut him down, you smile and accept the compliment. You aren't doing this for him. You're a golden goddess for you. And as long as that attitude is shining through (which I think it is, with you) then I wouldn't worry about how to respond. Whatever feels right in the moment.
I also just don't think that these WSs are so calculated in their every move. Some probably are narcissistic sociopaths and are carefully parsing out breadcrumbs calculated to keep you in the perfect spot. Others? Are confused messes right now and honestly don't know what they want. He could be breadcrumbing you to keep you as a firm plan B and make sure you're still in the game since he's sensing your distance. Or, he could be feeling a little pull and freak of yikes! I'm not ready for this and dang she is looking pretty hot these days, and that is why he said it. Or he genuinely knows what a difficult subject it is for you, and the compliment was intended to make you feel good. But all of that means you're parsing out WHAT he means and WHY he said it and HOW your response will or will not affect him. You are the best ever at not really caring about his BS... don't let this one area where you have some hang-ups get you down.
And work it, girl. For real.
May, you have no idea how much I needed to hear that it probably didn't matter a bit what I said in that one moment. My IRL friends got me with the confidence boosts about this new body, but a couple of them, well, they see everything he says or does as some kind of power move. And when I don't try to snatch that power back with my words or actions in the immediate they can make comments to the effect that he's like a border line sociopath and I'm a doormat. Even if I had wanted to in that very second take any little bit of power he had over me back and throw it at him, I was so caught off guard I had no chance of being that measured in my response. I've said it before. I can emote detachment like none other, hence a quiet thanks, shrug, and I walked away. But when he throws new leaning in behavior at me I get knocked off kilter.
As to not all WS's being calculating, or so calculating that every single thing out of their mouths, every action is planned is one of the most true things I've ever heard. My H isn't an idiot but we're in this mess because he has ZERO idea how to handle complex emotions, particularly difficult, layered, negative and/or confusing ones. There is no way in hell every thing he's saying or doing is thought out that far. But I know he does and says some things to to illicit a response so I try to be vigilant in how I respond.
