One thing I notice when reading CTO/CIOs' thoughts on their role, regardless of their experience level or how they attained the position, is that those who mention being "hands-on" – that is, coding or "being technical" – often lament that being good at their job prevents them from indulging in it. I find this sentiment telling, valuable, and a marker of a good technical leader.

Those who don't mention it might be good administrators, procurement officers, or even strategists, but they don't strike me as good technical leaders. Perhaps that's still being a good CTO, but I'm not so sure.

An HN user who is a CTO/CIO of some repute at a medical company (if I recall correctly) had a comment that has stuck with me (paraphrasing): the marker of a good CTO isn't necessarily someone who is in the technical minutiae, rather someone who wants to be in the technical minutiae; someone who is technically very curious.