I try to comment on most,,, but i think robert has a good point. for someone like me, I dont have a whole lotta time to sit and critique every single image (and there are a lot uploaded each day), so I click and view thumbnails that grab my attention. I do however make a point to comment on the ones I view. I have wondered the same thing myself. Everytime I post an image, I always type a message..... "please leave comments!!", but It doesn't always seem to work. Or, I get a bunch that say.. nice job, or good work, which are very flatering,, but hardly helpfull.