Comment # 13 on bug 1133876 from Maurizio Galli

(In reply to G�nter Halt from comment #12)
> "We could make a feature request. Does GNOME kill the processes at logout?"
> 
> pay attention: KDE kills not the processes too!

Yes I understood that KDE does not.  I was asking about GNOME and I managed to
test in a VM with openSUSE Tumbleweed, when I logged out processes were killed.

So to recap:

Xfce = does not kill processes
KDE = does not kill processes
GNOME = DOES kill processes

To be honest with you I'm not sure what the desired behavior should be but I'm
not keen to go touch systemd to handle this as I don't have the full picture of
what side effects it would generate