Every system that can be thought of (and has been suggested here) might sound great but when implemented at scale will no doubt prove to be open to abuse and require an army of mods to oversee. Otherwise every multi-million dollar social media company would have implemented it already.

Upvotes and downvotes and cumulative scores kind of do the job well enough that that’s what we keep ending up with.

That being said though, I would be interested in seeing a system where each downvote you make also counts against your own karma to discourage profligate use of the downvote to mean “I have a different opinion but can’t express it here”.