Comment 12 for bug 1013129

> How could a user who is set to autologin change their default session - without logging out, changing to the new session, logging back in and hoping it works on reboot?

if you never changed the session in a specific way for your user the default will be used, if you changed it you need to do what you describe yes, no need of the "hoping it works", lightdm will just keep using the session you selected until you change it

> Should they not expect that setting the default with either the sudo command or by editing the lightdm.conf file to do that for them?

no, if the default was overwriting the choices, since there is only 1 system default possible it would mean that all users have to use the same session ... what if you use KDE and your roomate on the same computer XFCE? why shouldn't you both be allowed to have a different default?