I think the key word is _constructive_.
I have read some snarky comments on photos and wonder if that person would have said that if they were face to face with the person receiving the criticism. I think likely not.
That being said, I feel that POTN is one of the most polite forums I have ever been part of.
I ignore the members/comments that aren’t very nice. On occasion I may have indicated that someone is being rude if I felt strongly enough about it.
I have to agree. I used to go to "ugly hedgehog" and I just got fed up with the rudeness. Not everyone, but it only takes a few. Mostly the long term members and "professionals". Someone would ask a question and I'd see someone respond with "Why not google it?". What is the point of the forum?? Also, many threads turned into political arguments even though not placed in the part of the forum dedicated to politics. And, as we all know political talks usually do, they would turn into nasty threads with name calling etc....
I rarely give comments or criticism unless I feel the member can handle it. When I do comment it is usually about composition and things of that nature. I try not to comment on things such as saturation & contrast because I've seen first hand how monitors vary drastically and what looks good on your monitor may look terrible on mine. Even my own devices, when editing for the newspaper & a 2x3 B&W print, I use my laptop, but when editing for a print for a customer I use my desktop w/ a 27" HD calibrated display.
At the end of the day, the only thing that matters is that you (or your paying customer) is satisfied with the image.