Ranks are handy mostly for coven leaders I think. Knowledgable members can see when people have been marked a fluffy, of course we would be more wary of letting them into the coven as someone has taken the time to mark them as such.
I would question them much more than if someone who was ranked a novice applied.
Of course, the system is flawed, and I have seen people marked as fluffy who should not have been.
I tend to use the system only when people are vocally fluffy on chat or in the forums, or to rectify a mistake when someone has been labelled fluffy and are simply new to their practice, or have had an argument with the wrong person.
Simply so coven leaders have something more to go on- espescially if that person has never posted on this site before.