Isn't this a problem, the single fact that, the negative feedback on an account can be removed only by the user might be a cool option but then, in the cases of the users dismissal and should it be that, it was wrongly given or without due reason, there should be a way to undo this. Ether by applying to admin or some other higher power in the forum. That's in the case of the absence of a user due to ban in contrast to the inactivity of an account or user.
For admins to get involved, that means trust is moderated to an extent which is not the case. If a user receives a negative feedback with no valid reason, chances are the user who left the feedback would not be on any level of DT and if they get banned from the forum, then their feedback would remain
untrusted, which is not readily visible to other members.
This is the most effective system, as any sort of moderation would require admins and mods to investigate and determine what feedback was right or wrong.