Sure but up voting their own posts is not the problem. The new problem is people posting any number of comments... often total spam and up voting their comment 100%. Sometimes not even bothering to up vote the post they commented on.
They can do this rapidly and have all of their rewards and the reward pool focused exclusively on themselves.
If there were two pools then the most they could take from would be the comment pool. It wouldn't effect the posts as well. Right now they are all in the same pool so it is draining that for everyone and even the posts themselves.
Oh ok that makes sense