I can't say that I've noted that phenomenon (balance of replies to images), but if it exists then it might be explained by the fact that people who have come to know/understand one another's minds a little bit feel more free to express opinion because they have an idea of how comment might be recieved. It naturally happens where posts are frequent and more personality is allowed to show through.
Equally, there are those whose posts are normally seen to be little other than ways of demonstrating imaginary superiority of mind, the smart-asses of this world. They usually drift away out of boredom... one hopes.
As for Micheal's 'Cover Shots', I've remarked before that some, that seem exceptionally good to me, don't attract that much comment, whereas others that don't say anything to me at all attract more comment. It simply goes to prove that tastes vary broadly on LuLa, and that's good, otherwise I, for one, might just as well stay home and gaze at my own site all night! I've seen enough of my navel, thank you very much.
I've had a second-thought: yep, I have noted that images of naked ladies do attract more clicks than do trees and rocks. Unfortunately, not so many of us seem to want to show our images of naked ladies.
;-(
Rob C