For Tesla’s Elon Musk, Twitter Is Sword Against Short Sellers

His extraordinary use of the social-media platform has often been followed by a jump in Tesla’s stock price, hurting shorts in the process

Tesla’s shares were up nearly 9% in after-hours trading on Wednesday following the company’s Q2 results, with the stock rising through parts of the earnings call. Here are some of the highlights. Photo: Associated Press

Fund manager Paul Wick says he braced for a hit to his bearish position in Tesla Inc. when Chief Executive Elon Musk on May 4 lashed out at short sellers in the auto maker, warning they were about to suffer the “burn of the century.”

He got it. Tesla shares jumped nearly 4% that day, leading some short sellers—investors who bet on price declines by borrowing shares, hoping to buy them back at a lower price and pocket the difference—to trim their positions, though Mr. Wick said he held tight.

...