Interesting trend. I have found a short article about it: https://www.odditycentral.com/news/south-koreas-fake-online-.... It seems nothing long-form has been written about it in English yet.

There is an overlap between Manifold and Polymarket/Kalshi. At the very least, Polymarket is more liquid, which creates opportunities for arbitrage and incentives for Manifold users to follow Polymarket. There is something at stake on Manifold itself if you choose to pursue it. There have been ways to convert mana to charitable donations (to your preferred charity), tickets to Manifest (the Manifold conference), and also merch and now prize drawings. Mana is like HN karma in that being at the top gives you status and bragging rights and suggests technical competence.