There's been a few comments on this thread about using the report button, that's fine in severe incidents or outright bad manners etc. but perhaps we should hear from the mods on this matter ad get their thoughts, I can see them being inundated with reports that are simply due to someone's ego not being massaged quite enough, or even being destroyed by negative comments.
Regarding crit, I agree totally with giving polite constructive criticism no matter how hard it might sound, how on earth is anyone going to improve if we are allowed to continue producing bad images and we are not told. However, I try to find a positive to finish with, this is pure common courtesy. Its important to consider how the OP is going to feel reading that their masterpiece is in fact rubbish, so politeness and considered wording is important, but equally important is that we do try to offer help or opinions and tell them why its rubbish and what we suggest to improve. Equally its important to give positive comments where they are due and give a reason why we like it.
The forum is a good one as Kipax said, but I disagree about it being right. You (Kipax) can go back a few years of your membership and I am sure you will agree that in days gone by, the standard and regularity of constructive criticism was far higher than of now, so is it wrong to try to reintroduce the same quality and enthusiasm. Its a shame that a good number of members from previous years no longer take an active part, and I a thinking of one in particular who had a lot of technical knowledge and was a huge help to me when I first started, and he helped numerous members to improve, and wrote a few instructional posts too. I am still in touch with him and he has said that he doesn't bother coming on now for just the reasons that have been discussed I this thread already.
We all have a preferred genre so tend to stick with the areas that we know, understand, or just like, that was the forum divides itself up into groups while still remaining a large gathering of like minded members. It would be unreasonable to expect anyone to comment in every area other than their favourites, but that is an advantage and not a loss to the forum in my opinion.