Sokka yells all the time, especially when he gets frustrated. But there's no more of that. No, Katara is now in the fore, and Sokka just can't be too angry when he's worried about his sister.

He shakes his head to Akito's question, but there's still doubt written all over his face. "Not sick, no. But..." But what? "She's been quiet. Just been preoccupied with things. And I'll bet you know from experience that Katara... is not some wilted flower of a girl. She's... look, if I can't get her hotheaded enough to throw water in my face with stupid jokes, I can't help but be concerned."