Elon Musk may have already been compelled to sell a sizable portion of his Tesla shares even if he hadn’t issued an unusual Twitter pledge over the weekend. Mr. Musk on Saturday polled Twitter users on whether he should sell 10 percent of his stake in his company. The poll appeared to be a response to a Democratic proposal to tax the unrealized gains of billionaires.“Much is made lately of unrealized gains being a means of tax avoidance, so I propose selling 10% of my Tesla stock,” he tweeted. Mr. Musk said he was raising the question because he does not take a cash salary as Tesla’s chief executive, and therefore wouldn’t have any way to pay a large tax bill without selling some of his Tesla shares, which make up the vast majority of his wealth.Mr. …
