There are some feedback like these example, so give moderator power to delete trust is necessary.
But it only waste moderator's time time unless the abused feedback is left by DT-1 or DT-2. I doubt people look for un-trusted feedback anyway
Look at untrusted feedbacks too they might be important.
A new scammer may not yet have been tagged. You should set it to be shown by default. When analysing trust pages myself a
credible rating is one with a
reference link and an
accurate description.
If in doubt
don't trade! unless it's affordable to you and you consider the risks and are fully aware of them.
If no reference is given, look at the name of the person giving the merit, their post history and their own trust page to see how accurate their trust might be.
admins and global mods can already moderate trust. I'm not sure why this topic is necessary? Are you wanting a "report to admin button"?