It's one of the few bright spots in their world, the volumes they can speak in silence, the way they can read one another. For Daryl, it's hard enough to admit and deal with his feelings; having to verbalize and discuss them, half the time, it's enough to send him back into defense. Which never goes well.

He half-smiles, tipping his head back slightly, a bit like a cat bumping its head against someone's palm.

This might be careful, but it doesn't strike him as fearful, it doesn't even seem like she's holding back. Maybe he doesn't read her as easily as he used to; or maybe he's just trying to adjust to thinking about this as, maybe, a when rather than an if, which is quite a ways from a maybe if things were just a little different.