Ted chuckles at Sherlock's joke. Ted himself definitely has a need to be agreeable, and doesn't rise to the bait when insulted, doesn't take it to heart. He admires Joan's resolve to not let anyone treat her any way she doesn't want to be treated. She's never unkind about it, just firm.

It's comforting in a way. He knows if he ever accidentally stepped over a line, she would let him know. He doesn't need to tiptoe around her feelings - and Ted definitely has a tendency of doing that.

"She knows how to take care of herself, that's for sure," he observes fondly, looking down at her. Which is why it makes him sad how frustrating it must be with the state she's in right now. But she's getting better now, at least.