Aww, c'mon erg, we don't really need that.
Just Kidding...Yes, you make some very good points there. In my "Screening New Members" thread in this section, I have to admit that I was not completely satisfied with some answers, while others were well-written concise replies. I think it really varies from poster to poster. Some people may have an opinion worth voicing, but do not want to take the time to write it all down. Therefore, they just write "we don't really need that, etc." but like you said, that's not helping the site at all if ideas are being stopped flat instead of changed and helped along.
For instance, instead of saying "yea erg tru dat werd lol" I wrote what I did. Hopefully from what I wrote and what you wrote new ideas will blossom, possibly helping to better this site.
Bottom line (please correct me if I'm wrong): Don't just post whether you agree or disagree, like or dislike someone's suggestion. Post a reason why and more importantly, post a modified idea or some alternative.
I am also aware that many "suggestions" are really bad. Those shouldn't be responded to with any of the above. :D
<EDIT> Damn it, DaKilla, you beat me to it...I wanted to say it first.
