Not that he wasn't already feeling comfortable enough in Natasha's presence to lower some of his guard, the fact he managed even the slightest of smiles is further proof of that. Steve can manage it and when he was in Louisiana with Sam and his family, it happened then. His defenses aren't fully lowered, he still tries to place those walls up ( but they're not a nearly indestructible metal like his arm, so they start to crumble after a while ) but it's a start to showing that he does actually trust people. It's less of a line of bullshit he sold to Raynor to make it sound like he was "healing".

"If you fall asleep, I'm just gonna think it's because you got too comfortable and not because of your company. But I am gonna have to get proof if you snore," he follows up a moment later, unable to keep the humor that was trying to peek through out of his tone. He'll leave her to wonder if he's serious about it or not ( he is, of course he is ) and whether or not he'll share it with the others or keep it to himself.

"I could eat some Thai. And you know as well as I do, I'm hungry a lot of the time. Perks of the serum and all." That time, his tone is dry because while that's at least one of the better perks not related to being a weapon used to hurt people, it's still a fairly inconvenient perk at times. "And does that mean when we get around to Bond, you'll be criticizing it the whole time?" He didn't mind a lack of reality in films, but he did look at things and think about how that weapon was all wrong for the scenario or how they were holding their gun like an idiot and why the hell didn't they have more knives on them? Yeah, he was gonna end up criticizing it too.