I've seen a few posts recently where people are using upvotes as validation that their opinion is the majority. It's lopsided without also having a downvote system, similar to how "Top" threads will rise up to the top but will never fall down without some counterweight. Some of the most controversial topics are getting bumped to the top without getting re-balanced by the dissenting opinion having a voice. I'm not sure if Reddit owns the concept of upvoting and downvoting, if that is the case than I can see why we couldn't have a similar system. People argue that it turns into an echo chamber but I'd argue that its even more of an echo chamber when the only scoring that counts for anything are those in favor of the topic creator.