[It really isn't going out of her way in Pepper's mind; she spends a good chunk of time there anyway. Still, she's glad to hear Bucky agree.]

Well, he also works pretty well with Tony. That requires some definite stubbornness. [Pepper speaking from firsthand experience. But the "never give up" attitude Bucky implies suits Steve pretty well. She's curious when he frowns, however.]

Is there something wrong with him not getting sick? [She's curious, not accusatory. Even without knowing his history, it's clear that Bucky cares about Steve.]