By Sheila Dang (Reuters) – Twitter Inc is facing a skeptical audience as it showcases its advertising opportunities on Wednesday evening at an event in New York City, three ad agency executives told Reuters, as the social media company’s plans under billionaire Elon Musk remain unclear. The Tesla chief executive, who is buying Twitter for $44 billion, has tweeted that the platform should not have ads so it can have more control over its content moderation policies. Twitter has told its employees in internal staff meetings and in public filings that its advertising business and other operations…