I hope it's clear from the opening paragraph that I would also prefer a downvote-free solution. I agree that I'm not really a fan of downvoting, but in our current system I think that it's a necessary evil or a lesser of evils, however you want to phrase it. This suggestion is seeking something that's possible with the tools that are presently available.

Rather than downvoting, I think it could potentially be more useful to somehow gamify ranking between posts. So you read N posts and put them in quality order without seeing anyone else's judgement, and then we can compare those virtual comparisons to the rewards to see how aligned they are.

I would probably prefer something like that, too, but the question is implementation. I don't know who would implement this, or how. Coincidentally, I recently watched a somewhat related video that talked about different forms of voting, including preferential ranking:

(And I downvoted the post to get in the spirit of the topic)

Thank you. Strangely, I was hoping that someone would. (and also that it wouldn't be too painful😉)