I had a DUH moment today. I didn't realize that I needed to edit the sort orders in the /admin/includes/language/english/orders_export.php file to align the proper datafields. I found the 'v_orders_comment' setting that you mentioned, changed to 0 and the duplicates disappeared.

Now to figure out how to prevent sorting so that the order attributes appear in the download file in the same order they appear on the printed invoice.

Looking good now. Knowing where and how to edit will make this very useful for almost anyone.