I suspect solving it is hard to impossible. You can heuristic anything as suspicious at a glance but moderation at scale fails. You personally can decide "this

I suspect solving it is hard to impossible. You can heuristic anything as suspicious at a glance but moderation at scale fails. You personally can decide "this review is bullshit" and block without issue but start flagging in a false positive or even true positive by a manipulator looking to start shit could cause considerable backlash as a futile attempt at pleasing everyone is made. Transparent and consistent rules invite gaming and opaque ones invite accusations of malfeasance and the uncertainty promotes bad feelings and bad behavior. Worse still is that even taking a stance to not take a stance because you know it cannot be done will bring backlash as there are many who demand you take their stance, even allowing easy distribution of self chosen block and filter lists are not enough. There are many who demand the appliance experience.