However, the soft delete gets the job done. In my group, we regularly use a soft-delete on finished conversations. They drop to the bottom of the list of threads, and the current threads stay on top. They’re not completely gone, but they are out of sight, which is just as good.
After you delete a thread, it’ll get a darker background and will have a "discussion deleted" note under the thread title. You can see examples at the bottom of this page (http://forums.ffshrine.org/groups/vgm-rumble-group-procrastination-station/).
Maybe Jessie, but probably an admin.
Highly doubt admins would take the time to delete threads that only you and staff can see.