Something that I feel is missing in this conversation is that IMO a multi relay architecture like Nostr is not trying to solve moderation or remove it altogether: it's trying to make activist moderators less relevant.
Activists, in this case, are people with a social mission that they deem it's more important than any other considerations: they think ideology K is dangerous and they are trying to prevent as many as possible recipients to be exposed to it. They will report you on Threads or Facebook to ban you, if you speak in favor of K. They will send e-mails to your employer. They will even send bomb threats to venues where you gather to celebrate K. If they are moderators, they will not only ban you if mention K in a positive light, but they will try to avoid other people from hearing K-speech as well. If they run a Mastodon instance, for example, they will have a ban list of other instances that are K-friendly, and they will make sure that, if you are using their instance, you can't see any posts about K. If you're curious about K, now you have to do the inconvenient dance of switching between two instances that in theory should be federated, but in practice are two different networks that don't speak with each other. This is good for activists, but bad for you, if you don't want to take sides on a culture war you don't really care about.
A relay-based architecture makes the work of activists a bit less relevant: they can still run their instance and ban every mention of K, of course, but now you can subscribe to their instance AND another instance that doesn't ban people who speak fondly of K, and they can't limit or control that in any way. In theory (and everything is a bit theoretical at the moment), relays that heavily censor certain topics are less preferable to a generic public than relays that don't do that, so activist moderators will pay their effort to shape discourse with less participation from users. Of course, if relays ban something universally considered bad, such as spam, they will have more success than if they ban some heavily divisive point of view that 50% of the public shares. In theory, these controversial actors can even advertise friendly relays without you knowing, and your client can decide to follow them transparently (the intent is "I want content from this user", the behaviour is "follow relays they advertise behind the scenes"). Of course they have to do that before they're banned, but the point is that, for every activist relay that tries to remove K from public discourse, there will always be one or more generalist or counter-activist relay that welcomes K, and you can choose to follow both at the same time, with the same client and the same identity, and nobody can do a damn thing about it.