If someone sent me that link but I did not have a lemmy.ml account, then I can read it but not participate.
If I have an account at lemmy.world then it's not trivial to find that post on that instance. I can't just edit the url because the post ID is not the same. I'd have to navigate to lemmy.world/c/[email protected] and find the post from that feed. This might be possible for recent posts but becomes very difficult with any posts even a little stale.
My understanding of "how lemmy works" is very naive, but I assume it's not possible to generate UUIDs for posts. That being the case you'd need separate lookup servers that maintain lists of urls for posts and can translate between them.
On this post, do you see the little rainbow Fediverse icon? Click on that. You're now looking at the original post on the server from which it originated. The post on lemmy.pethchat.org was federated to that server from lemmy.world where the post originated.
Go to the search tool on your Lemmy server, and put that lemmy.world URL in there.
The post will show up, and you can interact with it as it appears on your Lemmy instance.
Hope that helps! Let me know if you have any questions.
I would love to know this too but my guess is that there is no easy way to deal with this atm... A cross-instance guid don't seem impossible to me, but im also fairly new to Lemmy...
A link like [this](/c/[email protected]) will work for website users on instances with at least one person subscribed to that community. There is an open issues to generalize this so that clicking the link doesn't crash Jerboa, and another one to load data from the remote instance instead of just 404ing. I know that's not amazing news, but this is an open source project under active development.
Posts cannot be universally linked across instances as each instance has a different id, correct. I'm not sure anybody's thought of a way around that, even before considering dev time. Definitely a longer-term issue to tackle.