Ted smiles, and he feels like he's getting a clearer picture of Sherlock. He can imagine it would be rocky at times. Being a recovering addict, especially one with a brain like that, must make it hard to let people in. He's glad she's stuck with it, since it's clearly been to the benefit of them both.

"Well, I'm glad he has you. And likewise, that you have him," he says. He knows Joan cares about Ted, and that he can provide many things, but he doubts he could provide that kind of intellectual stimulation that her job and her friendship with Sherlock does. So it doesn't make him jealous at all, just glad she has that in her life.