John Carmack and Dave Cutler have always been individual code contributors, regardless of their titles and management responsibilities.

They never cut out management/executive duties completely (as in Mitchell's case), but they came somewhat close.

Carmack has been pretty explicit that he is not, nor does he want to be, a manager (either in the executive sense, or the “technical lead” sense). He sees himself more as a senior craftsman.

John Carmack did something kind of similar a billion years ago at Id.