Yes, it is fractured, and that is by intention. The point is that no one single person can control the entirety of the Lemmyverse. Suppose a spez comes along and tries to ruin things. Then, at worst, he can only destroy 1 instance. Even if he destroys the biggest instance, then it’s a big loss, but it’s not the end of the entire platform. Lemmyverse lives on.

As for how the fracturing affects the user - not much. As mentioned in other comments, each instance can communicate seamlessly between each other. I can post to other instances, and other instances can post to mine. All information is shared.

One caveat, though, is that the Lemmyverse is still very much in its early growth stages. So you’ll find a bunch of communities spread out over a bunch of instances that do virtually the same thing. It’ll look like the community is fractured. But over time, users are probably just going to settle on a single community, we just don’t know which one yet. Think of it like subreddits on Reddit. There’s basically always 3 subreddits about the same topic, but there’s always the one major subreddit, which is usually the one that you’re looking for. We haven’t reached that point yet - we’re still waiting to see which is going to be the “major” community for most topics.

Yes, and you can regard this as an advantage and a disadvantage at the same time: There will be larger instances where the iOS community will have more users than on other instances, and these will most closely resemble a centralized iOS subreddit. Sometimes it can be valuable to have discussions within specific parts of the community, though. For instance (pun intended), reddit is heavily dominated by US users, so European or Indian users might prefer to discuss iOS aspects within their separate communities, as some localized stuff doesn’t apply to US discussions. Maybe you want to have a place that allows piracy-friendly discussions and one that doesn’t. Maybe you want to have a local meet-up community that is more queer-friendly in focus than the main one. This existed on reddit as well, just that the subreddit names themselves would differ (r/ios vs. r/ios_piracy or something like that), and over here, it’s the instances (c/ios@lemmy.world vs. c/ios@piracy.net or whatever they’re called). That being said, in most cases, one community will very quickly win over the others for random reasons, if only one community is necessary, and the others might just link thereor something, like with subreddits that are called r/tearsofthekingdom vs. r/totk vs. r/tears_of_the_kingdom vs. r/zelda_totk etc.