With the rapid growth of open source and other geographically distributed software projects, more interface design discussions are occurring online. Participation in such discussions typically occurs via issue management systems or similar interactive discussion forums. While such systems have a low learning curve, they do not support key elements of design discussion such as comparing alternatives, maintaining awareness of the arguments for and against the alternatives, or building consensus. To better understand these and other challenges, we conducted a study of online interface design discussion. The study consisted of analyzing a large corpus of online discussion content and conducting interviews with designer and developer participants. We discuss the findings of our study and use them to motivate the implementation of an interactive visualization tool - IdeaTracker. The tool offers explicit support for tracking and comparing ideas and gaining an abstract summary of the overall discussion as well as specific alternatives. It also provides a voting system to support consensus building. The tool extracts and visualizes useful information from the discussions that would otherwise be hidden but without interfering with the current method of participation. Our tool is compatible with the issue management system of one open source project but can be extended for others. Initial user feedback is positive and confirms the need for an alternative visual representation of interface design discussions online.