Twitter said that it is indeed working on a way for users to edit their 280-character messages, although it says the project has nothing to do with the fact that edit-function fan Elon Musk was just revealed as the company's largest shareholder and now sits on its board.

source https://gadgets360.com/social-networking/news/twitter-edit-button-test-work-elon-musk-board-join-stakeholder-2865483#rss-gadgets-all