I am looking for a web forum solution that is organized exclusively by tags. Basically, you'd have one forum, and all threads would be categorized based on tags (pre-defined for my needs). In this community, threads may often overlap topic areas (tags), so being able to easily apply multiple tags (at time of thread-creation as well as modified later, as necessary, by moderators) is essential. Is this something either xenForo excels at? Or is there another product you are aware of that would work well for this?