I have a faint memory of reading something - an extension or a proposition? - that would let you downvote.

As someone else pointed out, you can't "draw" sats out of an account (also an obvious way to just get sats - downvote everything), and thus, "downvotes" in that mechanism would allocate those sats to another wallet, like a "donation" wallet . But again, if it was to the page, that would now incentivize the wallet this went to post or support to post controversial or bad content - it would gain from it.

There's really no good way. Also, "0 upvotes" is of course also a signal. I think what you're really noticing is that there is no way to balance out -controversial- content. But I'm not sure I'd want that; real pluralism means that I also want to read the things from people I disagree with, I don't want those drowned out/censored/deleted.