That’s very doubtful, seeing as since the post might belong to any of the multitude of instances, the api must send the instance name in the response to the client. The client’s host doesn’t figure in that. Additionally, the screenshot looks like the default UI, whatever it’s called (at least default for lemmy.world), and it doesn’t show the instance domain for communities on the same instance (at least doesn’t show currently).

But I’ll look into the JS hypothesis later. Weird shit is afoot there.