I've been meaning to add to this since I got to enjoy this position with an actual woman rather then RoboGirl. (Yeah, you all know who.
)
Here the expressions felt more important. Spanking doesn't stimulate like normal sexual contact, there aren't all those happy little nerve endings telling the brain how wonderful it is.
Even the pain part of it is more the brain getting keyed up via deliberate manipulation of the fight of flight response.
If you're really getting into the spanking it's more about the psychological aspect, and the expressions ARE important to that. The way her expression seemed VERY focused on my backside, the way I used my expressions, because where one moan is basically as good as another in normal sexuality a sort of wide eyed, open mouthed "Woah!" is understandable at the start, but once the adrenaline and endorphins are pumping and you've hit subspace... the way your brain interprets and responds to the sensations WILL change.
Now this was virtual so it's obviously not the same, but the ability to change my expressions helped make it a little less virtual.