Make only each account’s 5 most recent upvotes effect post rank. In effect this would make vote sellers need to make many more accounts to be useful, they would need to churn upvotes.
Things would move and change more frequently. Vote farming would be more obvious and make countermeasures easier.
At least that is how I imagine it would go.
Do the votes actually matter? They mattered on Reddit because of karma, although I never did understand the point of karma. What is the point on Lemmy? I rarely even notice the up/down votes on a comment/post.
It influences whether content appears on Hot/Top/Active