The sequence of events:
1. On a phpBB forum, a User posted a new topic.
2. The User then went in and began to edit his original post.
3. Shortly after he started editing, an admin moved the topic to a different subforum.
4. After the admin had already moved the topic, the User finished editing his original post and saved it. It was re-created in the original subforum.
Result: the identical forum topic was listed in two subforums (the original, and the place where it was moved). This caused some very bizzare and undocumented behavior. The forum admins had to edit the original code to prevent this issue from happening again.
Does WebWizForums protect topics from being moved that are being editd at the time?