Try to reason from first principles: karma is a property of a HN username. A username is attached to a human identity, even if not enforced. Karma is used to p

Try to reason from first principles: karma is a property of a HN username. A username is attached to a human identity, even if not enforced. Karma is used to predict future quality of that human's posts based on previous posts, and for it to make any sense it must be assumed that past quality is a predictor of future quality. Changing the human behind the karma breaks those assumptions, so it is a way of misleading the site's users.