What matters is if TF used the trust system in accordance with its rules. According to theymos,
On feedback pages, you can leave trade feedback. There are no rules for this
Therefore, TF can use feedback for whatever he wants.
If it becomes frivolous, then people will ignore TF's trust or the entire trust system. Action does not need to be taken by the trust system admins.
as said before TF is not in default trust list, therefore most people will never even see the negative rating.