Mark a thread as “unresolved” when the topic needs resolution, and mark it as “resolved” when you’ve achieved that state. There are also sidebar widgets to let you see all unresolved posts, optionally filtered to a specific tag.
We use P2 extensively at Automattic, for a variety of purposes. I improved Nacin’s code last November because I wanted a simple way to encourage the culture of coming to a resolution on a topic. All too often, conversations are left hanging. This is a problem for those participating, and an even larger problem for those reviewing the conversation at a later date.