I think Reddit is uniquely harmful to its users in several ways, maybe even moreso than Facebook:

- Users get an intense, one-sided parasocial relationship but with no upside of even communicating directly with each other

- The hivemind effect is very real, and using Reddit often gives people a very false sense of superiority of their knowledge on any given topics

- Misinformation is rife. Even outside of the conspiracy hubs. It's amazing how many of the "front page" posts are often misleading or slanted

- Astroturfing and content farming is even more prevalent but with less moderation.