The contacts list is just a single-spaced list of names after which are a few spaces followed by the contact's email address.
The "TO:" (forward) list is the same, only well, uh, "prettier?" There is a little blue box preceeding each name, then the name, and many spaces (not just a few), and then their email address. This list is double-spaced. I am noticing that since I deleted the doppelgangers, the "new" doubles are people I have emailed more than once. However, the first time it happened, all of the names appeared suddenly as duplicates.