The only person other than Carly Simon who knows the identity of her “You’re So Vain” lover said it’s definitely not David Geffen. Simon touched off another round of speculation over the 38-year-old mystery when she hid a clue in a new version of the song about the guy who walked into a party like he was walking onto a yacht. If you play it backward, you hear her whisper “David.” British newspapers concluded that meant Geffen, who was her boss at Elektra. But NBC Sports honcho Dick Ebersol told The Post, “I’ve never before spoken on this issue and I never will again . . . but I can assure [you] the David is not David Geffen . . . a really good guy.” Simon revealed the vain one’s name to Ebersol in 2003 after he bid $50,000 for the answer at a charity auction. He’s a friend of Simon and said at the time he made the winning bid “to make sure Carly didn’t have to tell a total stranger.”