It incentivizes homogeneity and greatly decreases the amount of discussion on controversial topics. If posts are permanent, tied to your identity, and potentially subject to legal punishments, people with minority opinions become much more skittish.

That could be considered only a risk if the moderation is bad, but bad moderation becomes more likely over time due to feedback loops. An optimally permissive moderator will risk inviting an overly strict moderator due to that permissiveness. An overly restrictive moderator will not. There is a greater likelihood of moderation becoming increasingly restrictive over time because the moderation narrows the pool of moderators.