@neo207 If you don't want an entire system to appear, delete the ROMS and gamelist.xml, but keep the system folder, as was said in this post.
If you delete the folder, the system will recreate it. It is not a bug: it is the way the system is configured to act, to avoid problems when the user accidentally deletes an entire folder (or deletes it intentionally and regrets it later).
@SkullGrin There is a known bug about games being deleted and still appearing on the gamelist, it has no direct relationship with how to delete a system, see this post: https://forum.recalbox.com/topic/21952/game-list-visibility-after-delete-roms