It appears to me that the current state of Lemmy is similar to other platforms when they were smaller and more insular, and that insularity is somewhat protecting it.
I browse Lemmy, and it feels a bit like other platforms did back in 2009, before they became overwhelmed and enshitified.
If I understand it correctly, Lemmy has a similar “landed gentry” moderation scheme, where the first to create a community control it. This was easily exploited on other platforms, particularly in regards to astroturfing, censorship, and controlling a narrative.
If/when Lemmy starts to experience its own “eternal September”, what protections are in place to ensure we will not be overwhelmed and exploited?
I agree, but the server owner imposing unpopular rules is not one of the two problems the OP asks about. Those are:
Decentralization with federated servers does not address those problems.
If the community becomes toxic, its easy to create an identically named community on another instance. A perfect example: when I joined lemmy I subscribed to the “news” community on lemmy.ml. When I saw how it was run, I unsubscribed and instead subscribed to “news” on lemmy.world.
Modlog documents all actions including moderator censorship. Nothing like that exists at reddit. If there is censorship happening, its in full view of the users on lemmy.
Again Modlog, if a moderator is removing dissenting opinion.
Beehaw is an example of a Lemmy instance immune to “Eternal September”. They disabled their easy signups, and defederated from instances that allow easy signups. I don’t particularly agree with their extreme approach, but its what was important to them and it was effective. This is a powerful use of Lemmy and the Fediverse.