The function of the Young-Girl is to transform the promise of liberty contained in the achievement of Western civilization into a surplus of alienation, a deepening of the consumer order, new servitudes, a political status quo. The Young-Girl lives in the same horizon as Technology: that of a formal spiritualization of the world.I can't figure out what that last sentence is supposed to mean, but I agree that technology is a prime culprit in lodging a higher degree of sensitivity to fashion deeper into our subjectivity. New communication technology -- smartphones, etc. -- allow for more self-surveillance and more access to the reassuring judgments of others. It amplifies our self-consciousness and our sense of the self as a performance. Identity doesn't drive our behavior but is the end result of it, a product. The "young-girl" epitomizes this, serving as a model (the "authoritarian commodity") that can direct the endless self-fashioning and give meaning to all the opportunities we now have to declare what we are.
"What we are" becomes a problem only when technology allows for it: Once we can mediate identity, we become aware of identity as a malleable, manageable thing, which of course makes our sense of self far more insecure. Tiqqun, I think, is using "young-girl" as shorthand for all the ways in which our sense of self is rendered more insecure in the social networks that are becoming more material, surveillable and elaborated. Subjectivity has insecurity built into it: "In the world of the authoritarian marketplace, the living recognize, in their alienated desires, a demonstration of power that has been made inside them by the enemy."
I think this is the legacy of the hipster, regardless of whatever new term comes into fashion to discuss them. The hipster is the authoritarian commodity that uses only soft power, regulating all who come into contact with it by inspiring feelings of inadequacy, disappointment, envy, boredom, etc. The effective hipster/young-girl signifies a plenitude of cool that it cannot actually possess but that nonetheless inspires a kind of hopelessness that you yourself will never measure up or be seen enough for what you are. The hipster/young-girl was the bellwether for the sort of subject that only understands itself through surveillance, through the assumption that its every desire is being judged, and that desire is pointless unless it can be displayed and surveyed. "Social" technology has made this sort of anxiety commonplace, the feeling that it's, say, pointless to read something if you are not going to Tweet out the highlights, or pointless to listen to something if Spotify won't notify everyone in your social network. I want to blame hipsterism for this, but they were merely the first victims of this more aggressive phase of the society of the spectacle. They were the first to see no alternative to seeing themselves as a commodity among commodities and to try to find the advantages of that, the pleasures.