LOGNAME="root" is still set in ebuild environment when using FEATURES="userpriv".
Portage should update value of this variable.
Some programs check this variable.
E.g. getpass.getuser() in Python standard library (https://docs.python.org/3.5/library/getpass.html#getpass.getuser).
I have a patch in the following branch:
I've posted it for review here:
This is in the master branch now:
Released in portage-2.2.16