> There can, I’m surprised no one has implemented this:

The reason is you're inappropriately applying an technical solution to a social problem.

You also make at least one critical error:

> As you contribute to thoughtful discussion, as determined by the diversity and ratio of up/down arrows

Upvotes/downvotes pretty much never measure "thoughtfulness," because for them to do so would require a level of social cohesion that would probably make upvotes/downvote unnecessary.