I define the worth of a person as the value attached by society to the enhancement of the interests and opportunities of that person relative to the interests and opportunities of other persons. One important form of enhancement of interest is the protection of the person’s life. If society regards two persons as being of equal worth, it means, among other things, that it is willing to do equally much to protect their lives.
This only follows on the false assumption that all life extensions are equal. If some people have a greater interest in continued living than others, then assigning equal value to the "enhancement of [their] interests" should fairly straightforwardly entail a greater willingness to "protect" the life of the person who would thereby gain more from it. We would still be "willing to do equally much" to equally benefit either person. But there's no reason to think that everyone benefits equally from the protection of their (respective) lives.
Nord thus seems to be repeating Harris' mistake of conflating the worth of a person (i.e. what weight we should give their interests) with the worth of a particular life-extension to the person. Recognizing that people have "equal worth" in the first sense -- that we should count their interests equally -- in no way entails that we should treat all life-extensions as having equal priority. Quite the opposite, in fact, if some life extensions are more beneficial to their subjects than others. Valuing their interests equally means preferring a great enhancement to one person's interests over a merely mild enhancement to another's.
Update: Erik Nord clarifies that by "interests" here he is talking about the psychological notion of feeling "interested" in an outcome, rather than the normative concept of one's welfare interests.