This needs to be a major concern for people...we're all getting taken advantage of by these voting-rings! ... However, I think I see a problem...

So you can make Alice's self-votes decay, and you can make Alices votes to Bob decay, but in a voting ring of n people, there are n^2-n unique votes before any decay occurs if they're smart about it...

You could conceivably make a weighted graph which describes the upvotes given in the last 24 hours or something and use some sort of network flow?...For instance Alice's vote on Bob's post is weighted by how much voting power has been sent/received by them from the same accounts?...idk It's a tough problem