Good job everyone blocking and boycotting .ml! It's having an effect, users are noticing and MAUs on their comms are falling!
And for anyone asking "Why are we boycotting/blocking lemmy.ml?" Here's a quick recap:
Lemmy.ml is an instance run by admins who are hardcore tankies and will enforce their ideology on their instance through various means from allowing (and pushing it themselves) propaganda (Such as Russia being justified in some way to invade Ukraine) and known propaganda outlets (Like RT) to removing content on their instance critical of their favored authoritarian regimes such as Russia or China and even banning users for such speech or speech critical of them if it's off their instance (Just like the Reddit mods of ol!).
If it was just some random instance it would have been defederated from long ago like the rest of the "Tankie Triad" (Hexbear and Lemmygrad), but they've positioned lemmy.ml as the "flagship" instance and abused that position and influence to become large enough to keep other instances from defederating from them.
Which I believe is harmful to the Lemmy-verse's overall growth and outside reputation. I have seen it come up before on Reddit threads (and other testimonials from people who came back and tried it again) that "They tried Lemmy but it was a bunch of tankies and went back to Reddit"
I don't know about you, but I'd prefer Lemmy to not end up with the reputation for being "Tankie Central " or even worse "Voat 2.0".
So if you haven't joined the boycott yet, join today and help us foster a better healthier Lemmy-verse!
You can take a look around here on !meanwhileongrad@sh.itjust.works for documentation of it or checkout this list of curated documentation
Unfortunately, lemmy only supports instance-agnostic links (like, that are written to link to a user's own home instance) to a community. It has no syntax permitting for this with links to posts or comments.
If you're using Firefox, you can install the Instance Assistant for Lemmy & Kbin, and it will modify pages on non-home instances to have a button in the right sidebar that will take you to the post on your home instance. With that, after you follow a link to a non-home-instance post, you can bounce to the corresponding post on your home instance.
You had it right originally. You can't do what he's asking for, which is unfortunately something that Lemmy doesn't support today. See my response to him. The exclamation syntax lets you make a link that, when viewed by viewers on different home instances, will take them to a view of that community on their own home instance. Can't be done (today, anyway) for posts or comments, which is what you're linking to.
EDIT: Looking on fedia.io, it looks like unlike lemmy, mbin automatically converts links to other instances to local links, without any special syntax. All of your links on fedia.io's view of your post are to views of the posts on fedia.io.
I suppose that mbin's approach might get a bit annoying if you want to link explicitly to the other instance, for troubleshooting or something, but I think that it's probably addressing the most-common situation that people want correctly.
EDIT3: And for completeness, since my own home instance runs a number of alternate lemmy Web UIs, and those could theoretically do the conversion in the frontend: