It's an interesting conundrum for sure, but I think a lot of people are looking at this the wrong way. People seem to want what they used to have on reddit: one massive community for each topic. In reality, federated services like Kbin and Lemmy are like lots of small reddits. Each instance has its own group of users and it's own magazines/communities.
This is a bit like how things used to be before gigantic sites like reddit were around. If there was a particular interest you wanted to follow or discuss, you would seek out a forum site that catered specifically to that interest. You might have a few different sites that you would log into to see new posts, add comments, etc. This fostered some pretty tight knit communities where you might actually get to know other users because they're might only be a couple hundred active users or even less.
And there might have been some overlap between those forums. If you're into cars, you might participate in one forum specifically for corvette owners and also a more general car enthusiast forum. Both of those sites might have boards dedicated to a particular model of corvette. The difference now is that you only need one account to participate in both forums.
And when a forum site would shut down, either the owners would give notice ahead of time so that users could relocate, or if the site disappeared, users were left to find new places to congregate on their own.
Kbin.social is a general forum whose purpose is to provide users with a centralized place to log in to to discuss a variety of topics. I think as the fediverse continues to spread, we'll see more specialized instances. Midwest.social is a good example of that that I am aware of.
So as it pertains to magazine ownership and faith in moderators and admins, is it really all that different from what we've been doing? If a magazine owner starts doing something that the community doesn't like, someone can create a new magazine and users can migrate if they choose. The same is true of an instance owner. In this case, I have faith that if Ernest decides to shut down the Kbin.social instance, they'll give us fair warning. And if the instance disappears overnight, I'll have to start over on another instance. The nice thing is that the communities that I participate in might be spread out. So just because this instance goes away, that doesn't mean that all my content and communities are gone with it. Merely those that were hosted on this particular instance.
I think the better approach would be something akin to multireddits where you could collect posts in similar communities from multiple instances into a single place. I believe magazines already have a feature sort of like that, but I'm not positive. That way, community posts would naturally be spread around to multiple instances and one instance going down wouldn't be the end of the world.