Modern desktops, like KDE, Gnome or Xfce don't support multiple concurrent
sessions by the same user on the same machine. Therefore, most Display Managers
(gdm, lightdm ..) will reject a second login by the same user. 
For the local session this is usually no issue as most people only run a single
seat. However, when enabling 'remote administration' in YaST, one can create
multiple remote sessions (using XDMCP).
Here any attempt to start a 2nd session is terminated immediately (not even a
warning is displayed). With 'autologin' active (the default on openSUSE) this
issue becomes even more prominent, as the default user will be logged in at
boot time automatically and therefore will not be able to start a remote
session (unless logging out locally) 

This has lead to numerous bug reports in the past, therefore this should be
release noted.

I'm not proposing any text as I'm not fully acquainted with the issues of
multiple concurrent sessions of he same user.

Maybe our enterprise desktop guru Frederic can have a quick look over a text
proposal.