The directory tree in the file browser pane is not sorted for drives other than the system root C: under Windows. For example, a directory containing folders named A-Z is sorted correctly when it is located on the C: drive. A copy of the same directory is displayed in seemingly random order when located on a network mapped drive Z:. See attached images.
The problem can be traced to this line: http://github.com/musicbrainz/picard/blob/release-1.3.2/picard/ui/filebrowser.py#L58
The behaviour of QtGui.QFileSystemModel is such that it only sorts directories under the path set by .setRootPath(). By using QtCore.QDir.rootPath() this defaults to the system root "C:\". This source http://bugreports.qt.io/browse/QTBUG-12934 suggests using "" instead.