Public displays are typically situated in strategic places like town centers, and in salient positions on walls within buildings. However, currently most public displays are non-interactive and are typically used for information broadcasting (TV news, advertisements etc). People passing by pay little attention to them. As a consequence, public displays are under-utilized in the everyday world. We are investigating whether use of interactive public displays might increase people's interaction with one another, with a resulting increase in sense of community. In this paper we describe the design and first deployment experiences of a platform-independent, interactive video commenting system using a large public display in two sections of a large-enrollment university class. Our preliminary evaluation suggests that students enjoyed the activity of commenting, that they participated a great deal, and that their sense of community was greater after using the system. We discuss lessons we have learned from this initial experience, and describe further work we are planning using this and similar interactive activities.