SAN FRANCISCO — Bright and early on Monday, Elon Musk sent the government a surprising new document.In it, the world’s wealthiest man laid out his possible intentions toward Twitter, in which he has amassed a 9.2 percent stake, underlining how drastically his position had changed from a week ago.Mr. Musk could, if he chose, buy more shares of Twitter and increase his ownership of the company, according to the document, which was filed with the Securities and Exchange Commission. He could freely express his views about Twitter on social media or other channels, the document noted. And he reserved the right to “change his plans at any time, as he deems appropriate.”It was a promise — or perhaps it was a threat. Either way, the filing encapsulated the treacherous situation that Twitter now finds itself in. Mr. Musk, 50, Twitter’s largest shareholder and one of its highest-profile users, could very well use the social media platform against itself and even buy enough sh …
