That's why we should be able to rate (up and down) the thread (the OP), not individual posts in the later discussion.

Saying that people downrate an idea just for the hell of it works both ways, i.e.:

Thread 1: "QQ Please Nerf Archer"
Thread 2: "QQ Please Do Not Nerf Archer"

According to that theory the same guy who downrates the first idea will also downrate the second. IMO it's a dumb theory.

Just limit thumbs up or down to OP, and show up and down count separately.