The post comments system is the reputation system. Literally all that's been changed is that that you don't get to see how much you have and that it's called something else.
You could argue that we should change those two little aspects of it back, but anything other than that and you'd be asking for things that we already have.
It's the 'ranking' system of it all that makes it go sour though, which is believe it or not is why it was removed in the first place.
Edit: If you want people to start using it more though simply start using it more yourself and it will encourage others to join in.
I give post comments as it is, and the most encouraging thing is receiving one myself every now and again.