Firstly, they discuss a bunch of paradoxical notions throughout the chapter, mainly I believe, about the duality of the self digitally and in the real world and how having both would de-value the uniqueness of the first. I think this is an argument that has existed before..."I think, therefore I am". The existence of a digital self does not take away the value and importance of the real deal person, if for anything else than the fact that without the original there would be no brain to transplant into the cyber-realm (for those people who considered the human body as "meat"...).
There are certain compromises between digital and physical selves, that reinforce the value of both, as well as each individual notion of identity. Physically speaking, we have the distinct ability to experience and grow as people through the things we feel, hear, taste, and see. Inversely, the digital realm's ability to transplant time, space, and eliminate the biases of gender, race and appearance create an equally unique social facilitation which helps the individual grow. What this means to me is the things that make digital identity seem real if not more vivid than physical identity are what we in fact, wish was better in our physical lives. That's why i see the whole digital self/cyborg/machine thing as an extension of humanity, made to assist, its not an evolution or a replacement. Technology is a crutch, people come down on it with the the dangers it possesses, but that's because humans are the ones behind it all. Some people will use a crutch to help them because they broke their leg and some people will beat others with it. It's all relative, I think.