Haha, that is an interesting article! I agree with you. In contrast to other platforms, people here tend to stick to their picture much more consistently. Probably because we feel and recognize that within this ocean of articles and comments the picture is the primary identification icon. Surely, the name is important too, but when we suddenly change the picture it might be that others initially don't recognize us because our mind somewhat is on autopilot not even looking at the name any longer but only the picture.
At least this is my feeling ;)
You are right about the username too. But ya when you are going through so many posts the circle pic helps.