Having read this thread and the many discussions on DVt (Described Video Transmission) audio that many people encountered and did not understand why... The answer is quite simple.. the highest rated (no.1 seeded)/lowest bit rated (file size) of this episode listed on all the major torrent sites was encoded (ripped/copied) and posted onto the sites with the DVt enabled. i.e. The files audio was encrypted with this facility on(playing over the top). You can think of it like someone putting a file up (with one audio track) that included the directors commentary. It is part of the audio file not a separate feed u can optionally select. I guess what I am saying is the No.1 downloaded torrent of this episode had a single audio track which (at creation) included the DVt overdubbing.
If u were watching through more legitimate sources you almost certainly did not encounter this issue as the Audio Tracks/Subtitles/DVts etc are selectable and available (when encoded) upon demand.
Hope this helps
MkIndyFan