I got a quick response on MDLSITE-234. Demo.moodle.org has been updated so that the Authenticated user role now appears in all the proper places.
According to the front page, the demo site is supposed to be the "latest stable release." In this particular instance, it was different, and I do not understand how the difference arose. IMO it is a serious problem in view of the fact that 4% of all moodle.org traffic goes to the demo site, and I assume that others go there for the same reason I do: to test new features
I created another issue into the tracker MDLSITE-235 "demo.moodle.org should always reflect the latest stable release"