I was thinking of this too but then you need to keep track of who’s allowed to vote and that’s weird thing to federate even conceptually.

Something along similar lines is how they do it on Slashdot where users are randomly assigned limited number of points to be used for voting which makes them more precious in general. Tildes is also interesting in that regard because while there are no downvotes there, trusted users can apply labels that serve as something between a reason for downvote and a report. For example comment can be tagged as „noise” for not bringing anything to discussion which automatically ranks it below other comments but not removes it entirely. This prevents jokes being the top reply which is nice. Nothing against jokes but it depends on what kind of content you want others too see on your platform.