I'm sure they have multiple accounts they can use to still give negative ratings or positive ones.
They actually have people on a default trust list where if you give a rating to somebody and you're not even in that list, it will not impact their rating but the information they've left is still available to the public.
It doesn't matter to me. The information left is still around and not exclusive from the public. With that being said, it's still possible to be slandered even by somebody with no default trust badge.