"Unlike my brother. I create my own personality. Personality is my medium." (23.54)
Neuromancer's identity is personality, something more human than artificial intelligence. See, computer programs are typically made to do one thing and do it very, very well. As people, however, we can change ourselves through learning new subjects, acquiring new skills, changing our mood, or altering our diet. In the same way, Neuromancer can change his personality in the same way—although jury's out on the whole diet part.