I don't understand why this isn't default behavior. I'm logged into kbin, as such if someone links another community on a different server, I want to interact with it through kbin, where I'm logged in.
While a browser extension is a great start, that doesn't help mobile users, so again it feels like it's something that should be in the base UI.
This is a great start though, and useful for those folks that can run browser extensions. Here's wishing mobile browsers had more extension support.