BuddyPress.org

I checked around and one of the cause could be this:
In the standard wordpress user profile page the membership plugin introduce a new field:
“Membership key” and the panel says: “This key is used to give you access the the members RSS feed, keep it safe and secret.” I think that all the ‘non-administrator’ users cannot access rss of the site without using this key.
The question is: “how must this key be used?” i can’t find related documentation. Can someone help me on this?

Thanks