Back in the 1990s, computer geeks half-jokingly referred to the Internet as “The Net of a Million Lies.” The anonymity it offered meant users could pretend to be anyone, and could say anything. “On the Internet, nobody knows you’re a dog,” as the famous New Yorker cartoon put it. Online anonymity today isn’t what it once was. But this weekend we learned how extensive — and how damaging — the Net of a Million Lies remains. While users of X (formerly Twitter) are allowed to use anonymous handles and write their own personal descriptions, the company’s servers are privy to...