Twitter is looking to encourage more private discussions on its service. CEO Dick Costolo would like to have a “whisper mode” that allows users to take public conversations and discuss them solely with friends, according to a video interview with Bloomberg. While the social network is public-first, meaning content is shared with everyone by default (unlike Facebook, where friends are the default), it does have a direct message (DM) feature for one-on-one chats. This potential new feature isn’t likely to replace that, but rather allow users to pick a tweet or set of tweets and use them as a jumping-off point to start a DM conversation with one of their followers. Interviewer Emily Chang got the CEO talking by asking about messaging apps, and noting that Costolo has previous discussed enhancing the ability to move between public and private conversations.