If defederation worked more like a shadowban, I would agree with you. .world defederating with feddit.nl could result in no one from .world seeing any content posted by anyone from .nl, but .nl can still see the content from .world. It's unfortunate that .nl couldn't participate anymore, but it's better than that community ceasing to exist.

Defederations as they exist now are like being in a restaurant. There are two employees, one makes the food, the other makes the drinks. It starts out with being able to order either, or both, right from the comfort of your table. However, the owner of the restaurant decides that he just doesn't care much for drinks, and kicks out the drink-maker. The drink-maker opens a new store across the street, but he does not serve food, only drinks, and the restaurant you started at doesn't serve drinks, only food. Yes, technically, you are still free to go across the street to get some drinks, or stay here for some food, but boy, wouldn't it be nicer if that owner never decided he didn't like drinks? Sure, not EVERYONE in the restaurant cares, but a pretty significant amount of them probably would. They might just go down the street to McReddits. Sure, the food there is pretty bad, but at least they can get both food and drinks without having to go across the street.

I never said I didn't understand. I'm pointing out a problem that can, and I believe, will, lead to issues with user retention. If one is punished for the bad actions of someone on their instance that they have no control over, it will lead to frustration. I know this because it has happened to me twice now- once with vlemmy disappearing due to someone posting something bad that spooked the admin, and now feddit.nl because someone posted something bad that spooked these admins. I'm not saying it's not understandable, I'm merely saying that a problem exists.

Yes, but I outlined my reasons for wanting no defederation. VLemmy was perfect- refused to defederate, actively moderated- until the issue with image federation spooked him. Also, saying "illegal content" is a bit meaningless on a globally distributed platform. On both instances- feddit.nl and VLemmy- many users outlined very similar rationale to me when the issue of defederation came up, and you and I both know that defederation is not used only for unmoderated instances. Lemmygrad is aggressively moderated and defederated from most instances because the owners find the political views expressed there distasteful, and that's not the only one.

It just introduces so much personal bias into the fediverse, where individuals who don't like Thing A defederates from instances that allow Thing A, cutting their entire instance off from it. Again, yes, you can join other instances, but that quickly gets annoying trying to find another instance that aligns with your Thing A-positive or neutral views. This is what I'm referring to when I say that it will kill the momentum- users getting frustrated and having to make multiple accounts to essentially dodge a completely unjustified ban (assuming they weren't the ones doing the Bad Thing that caused the defederation) will lead to burnout and lost user retention.

As I also said, there will certainly be an impulse to say "good riddance, we don't need them anyway", but I think it'll lead to more problems. The fediverse has existed as a small pocket of internet for a while. However, things don't shrink as easily as they grow. If lemmy continues to get time and money and resources poured into its development for an ever-shrinking userbase, it won't just go back to how it was. Growth is hard to undo.

I think this issue could be addressed on the front end.

The reason you would want a server that is federated with everything is so you can access all content at once instead of switching between accounts on different instances. If you could log into multiple instances at once with a single username and see content from both in the same feed it wouldn't matter if they are defederated. I think this federation thing ought to be, as far as possible, transparent to the end user.

The way this currently works feels odd to me - it doesn't really behave like a decentralised Reddit, because your account is tied to a specific instance and the content you see depends on which instance you pick. It feels like an awkward middle ground between a centralized service like Reddit and just having a completely separate forum site for each community.

Feddit.nl rules explicitly state no illegal content, so it seems to be not so much inviting illegal content as a failure to moderate account creation and post content, like OP alluded to.

It is a gung-ho way, but I understand why I'm being downvoted. People hear "I want to have the ability to view anything" or "I don't like being told what I can or cannot view on the internet" as "I want to view CSAM" or "I am actually a Nazi", which should result in an emotional reaction. It's just not what I'm saying.

In general sure, but not for problems like this. That wouldn't address the issue in the OP at all.

That won't change how we would handle instances with bad actors?

Absolutely agreed. I hope that becomes a feature soon, I know it is or was being worked on.