Hi, I've been having problems with this plugin. It seems to allow certain tweets through as comments, but doesn't display others. They are not being added to the moderation queue or filtered by the blacklist, they just seem to be dropped somewhere between getting the mentions off Twitter and posting them as comments.
If I delete the mentions which did get through as comments, remove the 'tmac_last_id' custom field from the relevant posts then force an update, the same tweets are found, and the same tweets from those are ignored. It looks like the tweets it's ignoring are retweets for what it's worth.
On previous versions the debug was showing the missing tweets, so like I say the problem seems to be with the plugin adding them as comments.