Like so many millennials, I entered the online world through AOL Instant Messenger. I created an account one unremarkable day in the late nineteen-nineties, sitting in the basement of my childhood home at our chunky white desktop computer, which connected to the Internet via a patchy dial-up modem. I picked a username, “Silk,” based on a character from my favorite series of fantasy novels, with asterisks and squiggles tacked on to differentiate my account from others who’d chosen to be Silks as ...