When I post photos I don't expect a lot of comments, I'm not looking for praise. I post pictures when I have something that people can look at and maybe learn something from it. Last week I posted a couple of photos in the people gallery "the two dollar studio" it was to show that good portraits can be done using one bare light bulb, nothing more than people using it as a learning tool. If someone types out a long explanation as to what the pictures are, then most of time it's like throwing out the smoke and mirrors to cover up the weakness in the photo. There are bad photos posted on here, ones that just can't be fixed, so other than just saying it's bad, perhaps I should just say, "I would have deleted this one so no one could see it". I comment on photos that I like, that are different and that are well put together. I don't comment on every photo, I don't look at every gallery, maybe some people do.
I can also see why people don't comment as it was mentioned in this thread earlier, they are new to photography and are concerned that what they say may be wrong, or that they aren't at a point where their comments would mean anything, as they don't know what could be changed to make it better.
I am sick of people whining and crying that no one looks at their photos, people do look, but they don't comment, and when someone does comment and says something negative, they complain and state that "you obviously don't understand" I understand that they have never been told no in their lives, and hearing something other than "you are great" just doesn't sit well.