Or think it differently. Imagine I have two accounts which I log in frequently. If I send negative feedback on Account A from Little Mouse account, I will not see that tag from my alt account and vice versa. Again, including alt in trust list is forbidden. In that case, would not tagging from both account be perfect?
Then you should probably make sure one of those accounts is never in DT (e.g. by asking theymos to blacklist it) and even then it's quite questionable if some users include both accounts in their custom trust lists.
Posting trust ratings - or supporting/opposing flags etc - for the same person from more than one account doesn't seem right. It directly affects the reputation of the target so basically creates an advantage for multi-accounters. I don't think that's the intent of the trust system.