Undo Convert | Tag - Filename fails to undo folder creation, i.e. the Undo doesn't remove the folders (if any) that were created by the Convert.
Also, I suggest Convert | Tag - Filename should (optionally and by default) delete any folders it empties. Currently if it changes e.g. oldfol\file.mp3 to newfol\file.mp3 and oldfol contained no other files, it leaves oldfol .