As a thought experiment, imagine three masks.  The first is matte black, with 0% specular and 0% diffuse reflection.  The second has a mirror finish, with 100% specular reflection.  The third glows, as an omnidirectional light source.<p>Would it be acceptable for a person in public to wear one of these, but not one of the others?<p>My sense is that if you want privacy in public, you should wear the matte black mask.