Currently, we have Support or no support and Agree and Disagree. We should add a neutral support and Both (Agree and Disagree if you what I mean) because people can agree on one thing but at the same time disagree on another thing...
Support for a neutral support rating - no for the both rating. Just don't rate the post if you agree & disagree at the same time.
Support for neutral support. Like Anna said if you agree and disagree just don't rate it. In fact, what you could do is reply explaining what you agree with and what you don't agree with.
Neutral Rating would be AWESOME! but having a "Both" and a "Neutral" rating would be confusing . Its either Neutral or Both button... I would prefer Neutral SUPPORT