Twitter Inc. said it’s starting internal testing of an edit button, and that work on the feature began last year -- before new top shareholder and board member Elon Musk polled users on the topic.

The ability to edit tweets after posting them has been the most-requested feature for many years, Jay Sullivan, Twitter’s head of consumer product, wrote in a thread elaborating on the company’s announcement. Roughly 74 per cent of the more than 4.4 million votes cast in Musk’s poll this week were in favor of adding the functionality.

Musk, 50, started the poll after disclosing Monday that he’d taken a more than 9 per cent stake in Twitter. He filed a new form with the Securities and Exchange Commission on Tuesday classifying himself as an active investor, a day after he was late submitting a form for passive shareholders. Twitter agreed on Monday to add Musk to its board.

Twitter posted a GIF on Tuesday hinting at how the edit feature would work. Sullivan, the consumer product chief, said the company would seek “input and adversarial thinking” before launching the functionality.

“Without things like time limits, controls, and transparency about what has been edited, Edit could be misused to alter the record of the public conversation,” he wrote. “Protecting the integrity of that public conversation is our top priority when we approach this work.”

Twitter shares fell 2.1 per cent to US$49.87 as the market opened in New York on Wednesday. The stock had gained 30 per cent after Musk disclosed his investment, notching the biggest two-day gain since the company’s 2013 initial public offering.