Twitter's Product Chief Leaves the Nest Michael Sippey, the vice president of product at Twitter, announced on Friday that he would step down from his position - the first high-level departure from the social network company since it went public in November. Mr. Sippey said in a letter to the staff, which he also posted on his personal Tumblr page, that he would transition into an advisory role with the company effective immediately, helping with product strategy and in the search for his replacement. "I've spent most of my career working at start-ups, helping them scale and having a direct hand on the product," he wrote, adding that he has had conversations with Dick Costolo, Twitter's chief executive, and Ali Rowghani, its chief operating officer, about the direction of the company and his career. And I've decided that it's time for me to move on. Mr. Sippey's departure comes as Twitter faces big questions about whether and how to change its user interface to make the service easier to use. Twitter's heavy reliance on text-based messages of 140 or fewer characters, displayed with the most recent first with no regard to importance, can be off-putting to newcomers. And even experienced users wrestle with information overload. Twitter has been reluctant to make any major changes to its design. But now that it is a public company, it faces pressure from investors to grow its user base more quickly. About 232 million people globally used the service at least once a month as of September, with more than 100 million using it every day. Mr. Rowghani has recently become more involved with Twitter's look and feel, particularly as it relates to how the service displays information about television shows, which are a growing source of advertising revenue for the company. Recently, Mr. Sippey was the center of an uproar over a change to how people on Twitter can block other users, which allowed them to view and send tweets to people who had blocked them. The change, which raised privacy concerns among its critics, was in effect for less than a day. "We have decided to revert the change after receiving feedback from many users - we never want to introduce features at the cost of users feeling less safe," Mr. Sippey wrote in a blog post on Twitter. Mr. Sippey joined the company in 2012. Since then he has had a hand in rolling out several prominent features on the network, including Vine, a short-video sharing service. "Like Tweets, the brevity of videos on Vine (6 seconds or less) inspires creativity," he wrote during Vine's release. In his letter to colleagues on Friday, Mr. Sippey kept with the theme of brevity as he noted his excitement for what would come next for him. "I hear this Internet thing has legs," he wrote.