The new thanks feature on Stack Overflow is terrible.
But there's a reasonable problem that has been identified: non-signed-in users don't get to say anything. For obvious reasons, we have avoided letting them change the publicly displayed score or cast votes which award rep.
But instead of letting the vote numbers pass into the void, we could simply display the number of <15 rep votes cast to the author of the post.
Or it could be a high-rep feature, like vote counts, which is fetched upon request. That solves the problem without putting too many confusing numbers in front of users who may not know what exactly is going on, and without introducing any new 'reaction'-like features which disrupt the user's flow.