Mitake, I accept your critisism of how this forum seems to work in your eyes, for if this is what you think then this is what you think (even if you only think this for the brief moment of having been really tired after a hard day).
But I don't think that your critisism is well founded.
Go look at other forums where there is NOT ONE WORD of critisism ever spoken to ANY of the photos presented, where everyone just praises any photo to the skies to underline their great friendships among each other and you will know what "no critisism at all" means.
But we clearly observe that all critisism is spoken in courteous manners.
And to look at a photo that does not appeal to us personally because it is far away from our style, or that does show technical imperfections because a) those were intended and thought over and used as a means of self-expression or b) because the (still budding?) photographer did not know any better (as yet) and to then say "Blah, this one sucks" does not help anyone.
Agreed: when someone posts a technically, compositionally or otherwise quite flawed photo with the introductory words "I think this one is my best so far", also I am at a loss of words sometimes and really no longer know what to say. To critisise an inflated ego will certainly lead to friction for that person (I am not thinking of anyone in particular at all!) will feel personally attacked. That situation could become tricky.
All in all though I feel that I often express in my comments when I am not too happy with something that shows in a photo. I prefer to "shroud" my critisism in questions to the poster, though, to make them think ("Wouldn't if have been better if ...?") . I guess that helps a lot more and does not leave bad feelings per part of the author of a (bad/not to my taste <- there is a difference!) photo.