In computer-mediated group communication, anonymity enables participants to post controversial comments without risking accusations of improper behavior. While this may encourage more open and frank discussion, it diminishes accountability. In addition, anonymous comments are perceived as weaker than non-anonymous comments. We propose a communication protocol that allows a user to send a strong message to the group without having to assume sole individual responsibility. The system posts an anonymous comment, and then calls for supporters. When sufficient numbers of supporters have been gathered, the system reveals the names of all supporters as a round-robin signature. This prevents the originator from being identified.