[:"pink"] But you can't make any posts in a category, because it contains several forums. In the Harry Potter example, you talk about Harry Potter in general in the Harry Potter forum, but spoilers will be posted in the subforum. The reason why it is a subforum because the posts in the subforum are related to Harry Potter, but the subfourm is strictly for posting Harry Potter spoilers.
If there was a Harry Potter sub-category in the Movies category, it would contain 2 forums. One problem with 2 separate forums is that there may be a higher risk of cross-posting (example: spoilers being in the Harry Potter general discussion forum).
Also here at threadsdev, the archived mods forum would work great as a subforum to the mods forum.[/]