What is your point even? If they are smart enough to erase their trail completely then you aren't catching them anyway. Again, what evidence is available would be submitted for public review. Neutral ratings could serve as warnings with the thread referenced. I agree "untrustworthy behavior is incredibly subjective", which is why I am arguing for an OBJECTIVE standard of evidence before negative rating. Account sellers could again be neutral rated with a reference thread. This is not covering it up. This is defining a very objective line so that the community can focus on fraud, not absolutely everything being perceived as subjectively "untrustworthy". The negative trust factory farmers would just have to find a way to get their dopamine hits elsewhere rather than from dropping negative ratings on people assembly line style and fellating themselves over the moderate amount of authority it gives them.
My point is that everyone that uses the internet is used to reading through bias and noise, restricting noise is going to reduce real valuable ratings. The current feedback system already works with public review. Most claims have reference links to a thread in question where a user can read more about the issue themselves. Poor feedback isn't insignificant either, it helps people follow patterns of who they should and shouldn't trust from feedback senders. The proposal here is to change the capability for tens of thousands of users, due to the actions of a half dozen people. They have their side of the story, and everyone else has theirs. Public review can take care of whether their feedback is significant or not.
Setting up rules so that people can't be jackasses just means that they'll find other ways to be jackasses. Let everyone put their worst self forward, and its not an issue.