Mainly that it only benefits giant instances. That's a convenient feature for people on a tiny instance following users on mastodon.social, but adds friction for users on mastodon.social who want to follow users on a tiny instance.
I haven't looked at the implementation, but I'll assume it's flawless. The issue is that it doesn't address the broader problem. Like the "official" iPhone app that has a giant, colorful "Join mastodon.social" button above a transparent "Pick another server" option, it serves to push people toward m.s and away from a good federated experience.
> I’m not sure I grasp the argument here. No feature should be switched on until all 23,000 servers have updated to the necessary version?
It's not about having the necessary version. The feature has to be cookie driven, right? Otherwise, mastodon.social wouldn't be able to remember that an unauthenticated visitor has an account elsewhere. Such a cookie almost certainly won't be available across servers (thanks, ad trackers for ruining it for everyone). That means a user would have to fill in that form for every single remote instance they visit.
Think of it this way: suppose a user visits a tiny Mastodon server at social.example.com. They click a user's follow button. How will social.example.com know to redirect the user to the home instance they configured when they visited mastodon.social?
> If I’ve downloaded the Mastodon app without having a server in mind what is the app supposed to do, just list them all?
If someone clicks the "pick another server" option, they're taken to a perfectly serviceable chooser. That should have been the default. It works for all the other apps that don't default to mastodon.social.
> That means a user would have to fill in that form for every single remote instance they visit
It looks like you're correct; I went looking and found that https://universeodon.com had the new feature as well, and I had to type in my home server URL again. I actually thought this was a great solution before I realized you'd have to do it for every server; hopefully they find a better solution for this.
If it worked that way, I'd support it completely! I think the idea is great. I just don't think it can be implemented in a cross-instance way, short of having some sort of central server.
With the feature the way it is today, it makes it a little easier to follow users on mastodon.social, and a little harder to follow users anywhere else. Suppose that hypothetical social.example.com instance has 1 user. If that feature's enabled on the server, anyone wanting to follow that 1 person has to complete that extra step with zero benefit. It's only useful for larger instances, benefitting the few centralized servers without helping the federation as a whole.
I haven't looked at the implementation, but I'll assume it's flawless. The issue is that it doesn't address the broader problem. Like the "official" iPhone app that has a giant, colorful "Join mastodon.social" button above a transparent "Pick another server" option, it serves to push people toward m.s and away from a good federated experience.