Idea: Pressing downvote triggers a prompt to reply to the thread or comment explaining why you’re downvoting, which is posted and the downvote registered. If you don’t create that linked post, or delete the post, the downvote is cancelled. Come to think of it, that wouldn’t be a bad idea for upvotes as well. If you’re not participating, why should you be able to vote either way?
Even simpler: no standalone voting. When entering a comment you are given the option to vote the post or comment up, down, or neutral. The vote is counted as long as your post stays up.
I’ll soon need to back on some of my optional subscriptions, but the yearly donation to EFF is staying for sure