A lot of valid and strong ideas here, this is my view point from having experienced two very different sides to renderosity... the the general population gallery and the forum.

As part of a forum group where we all comment, comment on each others work.. post images, set challenges,  help each other out when possible, we are all there because of one thing a "common interest" ART...no matter what way it is created and being creative, part of a community that you can draw ideas and inspiration from...A simple format...

The general population gallery, has a very different feel to it, it's very much each to their own, and i'm only going to comment on your image if you comment on mine, same with the likes and faves, same with the art charts, this no bearing on the individual skill level and so on...it's all to do with likes and faves how many view you have and how many images you upload on a daily basis, this is just a breeding ground for competition, 

The likes and faves has always been a part of renderosity and i don't see why that should change, i would like to see that hidden from view tho, so only the author of the image can see, 

I can see the need for more involvement, and the rewards schemes suggested maybe the answer

But ask yourself Why do people create art.....

Do they you do it to be rewarded because they have, that could just reinforce the situation that this thread is trying to resolve

I do it because i love to be creative and don't feel i need to be rewarded for something i already love doing, same with comments...i will and have always made comments on others work, even when i spent a year with comments off on my own work...

Constructive comments i've done this, it a very fine line to walk, 

So in conclusion.....

The solution is possible....back to basics, grassroots, we are all here for one reason"common interest" ART and the love of being creative and the creation of art, nothing more a simple format...