language performed for an audience of two hands
He’s still performing for her, syntax- and vocabulary-wise, at seventeen, the same way he did when he was ten.
Context
Orin diagnoses Hal's fluency as a broadcast with a single intended receiver: the whole prodigious syntax-and-vocabulary display is a performance aimed at the Moms, unchanged since he was ten, a boy still "performing for her" and living "for applause from exactly two hands." Communication routed so narrowly it has curdled into audition — speech whose real content is please-approve, addressed past everyone in the room to one pair of hands.