I understand. It really comes down to your entry point. For example, as long as I'm viewing the community/user/content via my instance I can interact; e.g. I'm replying to a post on https://mylemmy.win/post/114914 ; you, on the other hand are replying to https://kbin.social/m/fediverse@lemmy.world/t/158389/why-can-t-we-have-federated-identity . Since we're viewing from our own instances we can interact. If either of us goes directly to the canonical URL, https://lemmy.world/post/1194109 , we'd be forced to login. It's all the same post, just different points of entry that muddy the user experience.