I think they had some feature similar in the past like a reputation or kudos system, but it got abused and was thus removed. (may just be a rumor or I am confused with another forum)
It's a worthless feature. Just look how reddit works.
I foresee such a feature discouraging people from posting further once their idea of post in disliked into submission.
Trust me, these aren't the droids you're looking for.
I don't care for like/dislike systems. They are far too prone to abuse by jackassery. You'd end up with a system like disqus where up and down ranking means absolutely nothing. Ive actually seen good results from sites that use only a like option, but no dislike.
The only reason I'd like that is so I could click dislike on your post. It's a terrible idea, and you should be ashamed.