Mm, it'd be hard to enforce. Someone could write a review as a regular player and get promoted later on, for example. It'd be a lot of stress and annoyance trying to track down forum posts and harass admins about who might and might not be on staff.
I'm not a fan of staff writing reviews, personally, because it tends to be that glowing 90-100 "this is great, this is amazing, maybesomeofthisherecouldusesomework BUT IT'S SO PERFECT" type thingy.