At some point in Boulder Nick had realized that sign language was functionally dead. He could sign some, but not enough, and even if he could who would he teach? Who would care anymore? So he let it go, because there were a thousand bigger things to worry about, and he's always been good at that. Letting go.

So it shouldn't be a big thing, watching someone's fingers flicker meaning, but it grabs Nick's heart in loose fingers and then squeezes.

Yes, he signs back, after a moment spent remembering how.