Defederation is a double-edged sword

Agreed. It's not the solution.

The reality is that it’s a whole bunch of entirely separate environments and we’ve walked this path well with email

On this I disagree. There are many fundamental differences. Email is private, while federated social media is public. Email is one-to-one primarily, or one-to-few. Soc media is broadcast style. The law would see it differently, and the abuse potential is also different. @faeranne@lemmy.blahaj.zone also used e-mail as a parallel and I don't think that model works well.

The process here on Mastodon is to decide for yourself what is worth taking action on.

I agree for myself, but that wouldn't shield a lay user. I can recommend that a parent sign up for reddit, because I know what they'll see on the frontpage. Asking them to moderate for themselves can be tricky. As an example, if people could moderate content themselves we wouldn't have climate skeptics and holocaust deniers. There is an element of housekeeping to be done top-down for a platform to function as a public service, which is what I assume Lemmy wants to be.

Otherwise there's always the danger of it becoming an wild-west platform that'll attract extremists more than casual users looking for information.

Automated action is bad because there’s no automated identity verification here and it’s an open door to denial of service attacks

Good point.

The fediverse actually helps in moderation because each admin is responsible for a group of users and the rest of the fediverse basically decides whether they’re doing their job acceptably via federation and defederation

The way I see it this will inevitably lead to concentration of users, defeating the purpose of federation. One or two servers will be seen as 'safe' and people will recommend that to their friends and family. What stops those two instances from becoming the reddit of 20 years from now? We've seen what concentration of power in a few internet companies has done to the Internet itself, why retread the same steps?

Again I may be very naive, but I think with the big idea that is federation, what is sorely lacking is a robust federated moderation protocol.