User blog comment:DaNASCAT/Technical Update: November 6, 2012/@comment-4839035-20121106223538/@comment-1929113-20121107000503

Would it not be possible to create a usergroup with the  right that would make them not gain achievements anymore? The group could be able to be added solely by the user (and Wikia Staff I suppose), so it's the user's choice if they get achievements on their wiki. That does sound rather possible, and should be very easy for you to implement. It could also be a global group for those who want to be exempt from achievements across Wikia, which would naturally override any local decision.