I highly doubt Reddit will be looking at a fully decentralized system and could simply use it as an in-app currency with blockchain used to make it easier to manage.

I'm not sure how adding blockchain makes a centralized database easier to manage. In fact it just adds un-needed complexity.

It's a gimmick to keep Reddit innovating. Blockchain is the buzzword of last decade, and maybe for this decade, but we haven't seen it yet.