Thanks very much, Josette.  I shall.
It's probably by now a situation of Too Little, Too Late, but I did email MPI and expressed my disappointment over this matter.  Will it do any good?  More than likely not, but at least I expressed my views. 

   Below is the text of my email, for anyone who may be interested:
Thank you for releasing Dark Shadows on DVD.  I have fond memories of the show from younger days when it first went into syndication, but had missed many episodes, even when they were aired on the SciFi Channel.
However, I am writing to express my disappointment over the content in the DVD boxsets.  I did not notice at first but I have come across several instances where the episodes have been edited to remove extraneous sounds (such as off camera cues) or hide an a special effect that is not entirely successful, despite claims that the episodes are unedited.
I would very much like to know why this was done.  As a fan of the show for many years, I like my Dark Shadows "warts and all"  and I am sure that you have received other complaints of this nature as well.
Frankly, I avoided purchasing any of the series on VHS, because at the time DVD was in its infancy and I knew you would probably re-release the series in DVD format eventually. I understand that the VHS editions have not been edited in this way, and I am extremely disappointed to learn that I am not only getting the DVD series in a different format but also with different content as well.
I hope you will consider for future releases simply making the picture and sound quality as high as possible and refrain from any further editing of the episodes that remain.