When Elon Musk disclosed his stake in Twitter Inc., he had a choice.

Shareholders who intend to remain "passive” — those who don’t seek to influence or change control of a company — file a shorter form with the U.S. Securities and Exchange Commission, called a 13G. Those angling for board seats or seismic shakeups typically file a longer and more in-depth form, a 13D, within 10 days of buying their stake. The rule applies to anyone acquiring 5% or more of a public company’s stock.

Musk announced his 9.2% stake by filing the 13G. But the billionaire, 50, isn’t exactly one to stay passive. The chief executive officer of Tesla Inc. and SpaceX has called out Twitter for "failing to adhere to free speech principles” and the need to root out cryptocurrency scams that are prolific on the social media platform, which was cofounded by his friend Jack Dorsey. Musk is also among Twitter’s most watched users, with more than 80 million followers. Late Monday, he asked them — in a Twitter poll — if they wanted an edit button, a feature that many users of the platform have long requested.