He understands every word of that curse, grinning and almost laughing but keeping his hand over his mouth so she doesn't hear it. And then, in Xhosa:

"And that, ladies and gentlemen, is why I've vowed to never piss Shuri off. Ever."

There's an actual laugh from him at the comment about her mother, remembering her telling the story of how Reginald tried to buy Shuri and how even a younger T'Challa had told him he couldn't have his sister because she smiled and laughed and she was his to protect. He kinda wants to know what the Black Panther would do now in this situation, other than terrify Peter just by being his best friend's brother.

"I think mom is afraid he'll erase what she's become with him gone. She's been fighting his programming for weeks, and suddenly he's back."