It may well have to do with people commenting on the work of people they "know" to whatever extent. But there could also be the point of "being more likely to take the time to look at pictures I like" - which often means the ones the are in the direction my own work is, too, or perhaps where I'd like it to be. That would naturally lead to groups forming with different interests / tastes. And for me, it can also have to do with a difference between art and beauty that I feel. I love images that (to my eyes) are beautiful - no matter how much artistry there is in them. Perhaps I even admire a technically perfect scene without actually liking what it shows. But no matter how far someone has pushed Vue's limits and how much "art" his image is - if I don't like, I will not comment. Usually, I try to scan through the thumbs and if something catches my attention, I will look at it - regardless who created it. If I can think of something to say, I'll try to comment. But sometimes, I just can't think of a suitable statement - it's somehow pretty, but otherwise... don't know. Or with images getting dozens of "fantastic" and "superb" comments - who am I to make major negative comments? Possibly, I just didn't understand how wonderful this picture is? Personally, I'm grateful for comments on "how to improve that image". I may like that picture I made - and hopefully, I will still like it after reading the comments. But perhaps there really is something that could be better (also in my eyes) and I would have never discovered it on my own. I can be perfectly happy with just a couple of comments if they come from people who's own work I admire, for example. Or I discover the work of some people only because they left a comment and I get curious to check out their work.