From: https://forum.hackliberty.org/t/the-future-of-hack-liberty-and-the-death-of-federation/224

Problems with Lemmy

Data Replication, Moderation, and Abuse

All the data replication and moderation issues from Matrix also apply to Lemmy. This one of the underlying flaws of all federated services. Lemmy admins can be held liable for hosting illegal content that is being replicated over the federation. It also makes Lemmy servers easy targets to be taken down by malicious adversaries.

deFederation

Despite being "de-centralized", there is censorship in the form of "de-federation", which effectively removes "wrong-think" servers from the global audience on Lemmy. Even though there is claimed decentralization, a large majority of users congregate on the same few servers.

Censorship is hard, let the community do it!

Any posts that don't adhere to the Lemmy hive mind are immediately down voted, which is effectively a shadow ban that anyone can do by clicking the down vote button. Post that have any kind of negative score (two down votes) will be removed from the default post feed filters. (Active, Hot). This "shadowban" works to make it so 90% of the Lemmy population doesn't see your post unless they are filtered specifically for "new" posts.

Reddit and Lemmy are one big Psyop

The entire framework of both Reddit and Lemmy do nothing but help to promote group think and propaganda. Any posts that don't adhere to group think will be shunned and hidden. Post "scores" are a manipulation tactic used to influence (you) into being biased before you've even looked at the post. Manipulating upvotes and downvotes is trivially easy for really anyone, and it's abused by governments and corporations to create manufactured consensus and trick you into believing that the "herd" thinks a certain way. Of course, having a lot of upvotes appeals to the most pathetic of egos, and the psyop continues with more incentivized group-think posts in a never ending cycle of garbage user generated content.