Michael Platt’s Highly Leveraged Fortune Balloons to $11 Billion

Michael Platt made his first billion charging hedge fund clients fees until ditching them seven years ago. Now, without the same constraints, he’s spun that bundle into one of the biggest fortunes in the world.

But just how much Platt commands — and how much he deploys into markets — remains a source of intrigue across Wall Street. He stoked it a few years ago by sliding into the backseat of New York’s “cabbie to the stars” and boasting he was the highest-earning person in finance. Platt later dismissed the viral social-media interview as spoof.

Remarkably, the absurd episode ...