Constructive criticism is entirely different -- if you played through a mod and noticed issues with it, or maybe there was something about it that you think could have been improved upon then that is where the pos/neg feedback is essential as it is not only helping the modder but is also helping to get the mod fixed and re-released. That's my 2 cents on the subject.
Not everyone takes criticism lightly... Or even at all.A good example was of this.long lost mod called Cathalan. I never commented on it in the WIP thread but I will admit it did look enticing. However, said modder did not seem to be open to actually improving his mod. If I remember correctly, there were a number of us who suggested valid changes, but he pulled out the ol "If you don't like it, then don't download it" card.
Okay, I understand that, but what's the point of starting up a WIP thread and gathering attention and input if you're only doing it for yourself? Maybe this is just me, but I mod to try to find a middle ground - something I like that I think other people will like too. That's just me talking realistically about my philosophy. For other people it's about artistic fulfilment, or a bunch of other reasons - those of which I don't understand.