Currently, guests and hosts who break AirBnb rules and are found at fault in a dispute are still able to leave negative reviews. As long as they don't specifically mention that an AirBnb investigation was opened against them (by explictly mentioning the case number or name of the AirBnb customer service person involved) or attempt to extort their host or guest into leaving a positive review or dropping their complaint entirely, they are free to say whatever they want (including blatant lies) in their review as retaliation against being found to be at fault. This policy means that guests and hosts who have had negative experiences at the hands of these individuals have to choose between getting help from AirBnb customer support to resolve the issue and risk recieving a retalitory review, or to stay silent.
Guests and hosts who are found to have broken AirBnb rules or are found at fault in an Airbnb dispute should not be allowed to leave retaliatory reviews. After they have been found at fault, the option to leave a review should either be removed or their review should be subject to extra scrutiny to ensure that it is not penalizing the victimized host/guest for making a valid complaint.