You are commenting on a LemmyNet post from the shit just works instance. I am replying from a LemmyNet account on lemmy.world. It could also happen that someone from a Mastodon instance could reply to this comment. Everyone can have their account on a specific instance (even self-hosting their own instance) and still be able to see content from other websites. There is no singular website that hosts all data and there is no singular authority (ok maybe you could argue the developers of the software, but it’s also open source and other options do exist so it’s not a true single point of authority) for the entire network.