Well, one pc, 2 steam accounts each with its own Dayz.
Log in as user A,
join a server,
Log out of Dayz and steam
Relog as user B
and you can see the player name/character issue straight away, I'm sure this is not new.
Get user A whitelisted on a server
Join the server
Log out of game and Steam
Relog as User B
attempt to play whitelisted server. (it may ir may not let you)
play dayz 2 or 3 times as user B logging in and out of Steam each time
relog as user A and attempt to join whitelisted server, you won't be able to.