I have not been able to repro this, no. Been checking a few different sites every few days over the last week, never seen duplication other than the second entry for my own user.
@Rob_Jeffrey, the screenshot you shared shows your user duplicated (as expected - it displays at the top for you and then later in the list where it is “sorted”). However, I don’t see you appearing a third time, nor any other duplicated users. Can you share a screenshot that shows the unexpected duplication? Also, how new is your site? Is it by chance a recent install?