SAN FRANCISCO—In an effort to make the platform a more civil space, Twitter announced Monday that it would promote healthier discussions online by allowing only one user to tweet at a time. “Imagine you were having dinner with five or six friends and everyone just spoke at the same time—it wouldn’t work, because no one would be able to understand what anyone else was saying!” said CEO Parag Agrawal, explaining that the situation was even more complicated with Twitter and its approximately 400 million users, who under the new policy would each be added to a central queue and given a chance to send one tweet as soon as their number was called. “What we want to do is take that basic concept of a conversation among friends and scale it up to accommodate our entire platform. So we’ll let one person tweet, pause to make sure everyone has a chance to read it, let a second person tweet, pause, and so on. Though wait times may extend years or even decades, we think users will be more than willing to tolerate it after they see how elucidating the discussion is.” Agrawal added that while users would no longer be able to like or comment on a tweet, which would be too disruptive, Twitter would add a “raise hand” feature so that the one person tweeting could call on that person to hear their input.