You should be using !asklemmy@lemmy.world type links instead of direct URLs. If I click, it kicks me out of my app to where I can’t subscribe as I’m not logged in to that server.
Using !community notation is a Lemmy-only thing. Not everybody is reading this from Lemmy, and this particular community and the OP are both on /kbin. Providing direct URLs is a more generally useful way of linking to communities in the fediverse.
@Tygr@herpderpedia Kbin does not support !community links just yet, but it's in the works on some level. Linking to Lemmy communities from here can't really be done without the full URL, which does mean one would have to provide two links - one that works on Kbin, and one that points to the original instance.
In related news, linking to Kbin magazines is currently a bit borked as well, because the only other syntax that works (@magname) is assumed to refer to a user account and not a magazine.