Yes it ignores duplicate links for page rank as far I know, but I saw no difference if I had two links point to the same page and marking one of them as nofollow. The page pointed by the link had rank. That was a while back when I did the test with internal links. It may depend on the current algo they use. For example if they filter duplicated links and then process only the first link, then the position of the nofollow link may play a role.