When I use the move & rename options:
1. Picard moves and renames the files to the new location desired
2. The original directory from which Picard read the file(s) remains visible, but becomes inaccessible, even with administrator privileges.
3. After exiting Picard, the directory is no longer there.
Apparently Picard deletes the directory when the move and rename completes, but does not release the handle until the program is terminated. Until then, the directory continues to be visible (although inaccessible) in Windows Explorer and in 3d-party file managers such as Windows Commander.
Perhaps the handle could be released sooner, so that the changes to the directory structure would be visible immediately, instead of after closing Picard.
For details please see this thread:
http://forums.musicbrainz.org/viewtopic.php?pid=26623

P.S. It seems that this behavior is not reproducible. In my use of Picard today, the above behavior occurred several times. However, in several cases, Picard behaved as it should. That is, the emptied directories were immediately deleted (as shown by Windows Explorer and Total Commander), while Picard was still running.