Why do you keep talking about 'credentials'? Its not like you can have a certified degree in D&D. D&D is not competitive by nature, so it can't be compared to poker or MTG.
I'm not @ad_hoc, but the point here is Treantmonk is being appealed to as an "Expert" or authority in arguments in this very thread; and he is really no such thing. He is certainly not a beginner, and he has taken a lot of time and effort to post his opinions on various things D&D related, some of which I and many others agree with, but that does not make him an "expert"; or at least not in the sense that simply stating: "Treantmonk says X" wins any arguments as an ultimate appeal to authority.