Twitter Inc. said Friday it will not block world leaders from its social media platform because they play a critical role in global and public conversations. The statement comes after some Twitter users have called on the company to ban President Trump for tweets that they say encourage violence, even stoking fears of a nuclear war between the U.S. and North Korea. "Blocking a world leader from Twitter or removing their controversial Tweets, would hide important information people should be able to see and debate. It would also not silence that leader, but it would certainly hamper necessary discussion around...