Is that reference to "second nature" from John McDowell? Anyway, your point strikes me as merely semantic. If you define "natural" broadly enough, then sure we're natural. But calling personhood "second nature" just because it's familiar to us doesn't make personhood (our autonomy, intelligence, consciousness, morality, culture, etc) natural in all respects.

I explain in other articles the sense I have in mind: morality and personhood in general are unnatural not in the sense of being supernatural but because they're antinatural. We prefer artificialities to wildness. Morality isn't as wild as natural patterns. On the contrary, morality is as gratuitous as decadent culture, so that makes it part of an effective revolt against nature.