In our old forum software we had to create a hidden forum called our "Archive Forum" as a way to document bad behavior of users in case we needed it for legal reasons later. But it just struck me ... the option for Soft Delete (Leave deleted post) ... seems to accomplish the same goal without having to move the post to another forum.
Is that what its for?
Also, do deleted posts stay searchable (or at least are they on the "view user posts" link) in case we need to go back and find them? Is the content of those posts searchable by keyword ?