I think this definitely answers "what is blockchain good for". It will allow subreddits to monetize effectively and encourage users to post quality content using economic incentives.
Notice the higher signal on Hacker News, with no compensation, because high quality contributors want to contribute with no compensation and moderation is consistent and intentional.
Quality content, properly understood, is almost always created because of other-than-economic incentives. In actuality, economic incentives are in conflict with its production, and quality only emerges with the economic incentives are (at least partially) subdued.
I thought we had already arrived at the answer to that: "nothing (good)"