There needs to be a system in place that would allow mods to be properly measured in there ability to handle reports fairly and properly. I very much doubt that there is some one who consistently looks over every report and evaluates if mods are making the correct verdicts.
Why not implement a way to allow the community to "vote" on the end report verdicts and let the players decide if they believe the decision is fair or not. This would prevent any sort of mod abuse and allows the people who run the site an easy way to evaluate wether or not the mods are doing there job well. This also would be helpful for mods in the appeal process, as mods would be able to read the results and if the overwhelming majority of people believe the verdict given was incorrect, they know that the report needs to be reassessed.
One possible way to do this would be to implement a poll after a report decision has been made. Mods would still have the ultimate power in the final decision, but at least this way we give the community an easy route to help improve and monitor the site.