Right now retweeted messages are not displayed, which is understandable, however their presense affects how many messages are shown in total. For instance, if someone has retweeted five things in a row, no messages will appear on their twitter module.
example (at least, at the time of writing):
http://twitter.com/MasashiHamauzu http://vgmdb.net/artist/145
ideally I would think it'd just ignore the retweeted messages and show their last 5 regular messages/replies.