Hi Ian, Vanessa from Peer 2 Peer University here.
While I think your concerns about validity and authority are solid ones, and design does influence perception, I wonder if you could see it another way…
P2PU has designed our Badge system to optimize feedback and interactions between peers in reviewing Badges. So, in this system, the Badge matters less than the feedback and evidence behind it. What are your thoughts about cognitive authority and legitimacy in light of prioritizing not the way the Badge looks or the metadata, but the meaty stuff in the interaction around it?
A sample to give you an idea: http://badges.p2pu.org/en-us/project/44/