Open innovation and crowdsourcing rely on online collaboration tools to enable dispersed people to collaborate on creative ideas. Research shows that creativity in online groups is significantly influenced by the interaction between group members. In this paper, we demonstrate how theory can be effectively used to design and evaluate a tool for creative online collaboration. Specifically, we use the body of knowledge on creativity support systems to inform the development of a tool to support anchored discussions. Anchored discussions represent a new mode for creative interaction. In anchored discussion every comment is tied to some aspect of an idea. We evaluated the anchored discussion tool in a laboratory experiment, which generated insights for additional and refined research. Our results indicate that anchored discussion leads to a more structured discussion amongst group members and consequently to more creative outcomes. In a post session survey, participants made several suggestions on how to improve anchored discussion. This paper concludes that anchored discussion is promising as a new tool to aid online groups in creative collaboration. This paper extends a previous version presented at CRIWG 2015 [Link, 2015].