The stock of Icahn Enterprises LP IEP tumbled 21% Thursday, a day after billionaire hedge-fund manager Bill Ackman, founder and chief executive of Pershing Square Capital Management, revived his longstanding feud with Carl Icahn in commentary on a recent short seller report. That report by Hindenburg Research accused Icahn’s publicly traded investment vehicle of inflating asset values and and causing his company to trade at a large premium. The report has cost IEP some $10.9 billion in lost market cap including Thursday’s move. Ackman taunted his rival by reiterating Icahn’s oft-quoted Wall Street saying that if you need a friend, get a dog. “Over his storied career, Icahn has made many enemies. I don’t know that he has any real friends. He could use one here,” Ackman wrote in a lengthy tweet. For more, see: Bill Ackman resurrects billionaire feud, saying Carl Icahn needs a friend

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