Default instance blocks should largely replace defederation
Since what content users might want to see is quite unlikely to match which servers the admins tolerate, choosing instance on the Fediverse can be quite complicated, which is inconvenient and off-putting for new users.
For this reason, and simply that the Fediverse is stronger united, I believe defederation should ideally be reserved for illegal content and extreme cases. If Fediverse platforms would allow instances to simply block the rest for users by default, the user experience would be the same, unless they decide otherwise.
Just because few people can see it in the home instance doesn’t mean it isn’t there. And when a community is viewed from remote instances that have a different soft-defederation list all the bad stuff will be publicly visible (and indexed via search engines).
So for example a feminist community would be full of incel posts that are publicly visible almost everywhere.
Okay, that’s entirely fair. I was mostly thinking about the microblogging side of the Fediverse and didn’t quite consider the complexity that it would add to community moderation. I guess better moderation mechanisms could probably account for that, but Lemmy is as of now far away from that.
Edit: One might also solve that by not allowing soft defederated users to post in local communities.