Personal Experiential Influence:
It also seems to me that expertise and authority also has to do with the love attributed to craft by a practitioner. The presence provided for tasks at hand. If you do not love the work, or if you are not present in practice, your auhority and expertise are diminished.
Yes, when we walk into an office or other environment an it is full of books, diplomae, notes of thanks, and so on, we may be influenced to believe that the person in front of us is both experienced and of a certain authority. But if in the next ten minutes the discussion washes the diplomas from our thoughts and replaces them with feelings of doubt or even regret due to the way that the conversation has progressed, no amount of books with return the original superficial feeling of expertise and authority. Mediators are no different – the quality of their practice will most likely benefit most from a healthy regard (love) for the practice itself.