I'm on kbin.social and participate in communities across ~20ish other instances regardless of whether they've turned off registrations temporarily or permanently. Disabling registrations only prevents new accounts on that instance, it doesn't stop people from posting and commenting from other instances.

Parent comment is the perfect example of how we got so used with dealing with shitty and user-hostile systems. We've been dealing with walled gardens for almost a generation now, it's like they don't even understand that it is possible to interact with a remote system without having everything in one centralized database.

People have forgotten how email works.

Gmail isn't a walled garden but it doesn't have a 20k user limit

It would have if they were not profiting of all your data.

Besides, that's not the point. The point is that you don't need to have a Gmail account to reach and be reached by Gmail users.

I think what the parent is alluding to, is the fact that, Googling something and ending up on a Lemmy instance that is not your local one. You can, in fact, not comment on these instances. You must access it through your local instance (e.g. lemmy.world/c/[email protected]).

It won't be long until someone makes an extension that can detect AP servers and lets you interact with remote instances using your own.

A browser extension? While I agree, the client (browser) probably has to know about ActivityPub, or store some state that sites can read (without third party cookies), it's not fair to expect users install a browser extension for what would be basic functionality in their eyes.