Musk suggested the platform was crucial to civilisation and should be an inclusive place where people could watch everything from porn videos to family-friendly memes.
The post came shortly before Musk's US$44 billion ($75b) deal to buy Twitter was set to close, in keeping with a deadline a Delaware court imposed.
University of Richmond law school professor Carl Tobias told News Corp that Twitter was already having trouble making money before Musk "battered it and litigated it to death".
Musk on his Twitter page described himself now as "Chief Twit".
Last week, The Washington Post reported Musk intended to lay off most of Twitter's workforce if and when he became the social media company's owner.