This discussion (which started with just documenting what you could do at
the login screen) has certainly taken on a life of its own.

For my own needs, I'm not concerned about multiseat, but recognize that a
few (probably very few) others are.

I suppose if you really want to protect against a single user shutting down
or rebooting, you'd have to disable magic keys. Many distros have done that
- one of the first things I do after installation is to enable this
feature. I should point out that this neat little trick will work under
just about any circumstances - if you've got some runaway process eating
99% of memory and want to force a reboot, this should kill it. Generally,
it's better to resort to magic keys, as opposed to hitting the reset button
or pulling the wall outlet. Magic keys are supposed to terminate processes
in an orderly fashion, which is not the case when you pull the power cord
from the wall.\\

About SLIM as a display manager - I'm fine with it, even if it's not really
maintained. The important thing is that it's fast, stable, not riddled with
security holes (including systemd). I'm open though to changing to
something better, if there is something better.

cheers,
Robert