oh right. Well here's the post I was talking about: https://lemmyverse.link/feddit.nl/post/31396342 ๐ Thanks!
Thank you all for explaining.
The behaviour I was expecting was to click 'login' on the feddit.nl page, and that login page to recognise that I was logging in with the credentials used by lemmy.ml, and to log me into lemmy.ml instead, and then to be redirected to the 'local' version of the link on the lemmy.ml instance.
Rather than it just be a feddit.nl login page only, and be told 'log in not recognised'. That's where my confusion came from. I'm like "wait, I can't log into Lemmy here? why?!"
Ooooooooh I see! right.... yes that works.
I wasn't familiar with the idea of the instance 'fetching' a post. Thank you!
Thank you that is useful to have that explanation here. I had no idea it works like that!
I've not seen this type of logging in issue within the Mastodon 'world' because no one's ever 'sent me a link from another instance and then I tried to log on from that link' ๐. I just tried it on an inprivate browser window and of course it's the same as what I found here with Lemmy - as you described. With Mastodon I'm on the .social instance and I can see and interact with posts from any other instance - but after your explanation I realise that's because the content was alwasy served up from within the instance.
[I agree that with ActivityPub we certainly cannot expect to log in with the same handle *between *services (i.e. use your Mastodon handle to log in to Lemmy). Although that would be cool. Persistent IDs across the fediverse would be the dream imho (like Nostr does it).]