As much as I agree with this, are security and single-user truly mutally exclusive, or is it just that all the single user operating systems we know of (correct me if I'm wrong) have poor security records?
Absolutely. I'm not saying you can't build it, I'm just saying that P(correct security | correct multi user) > P(correct security) because you already have an isolation mechanism in place.
Not necessarily. You can design your isolation system to be better suited to a single user system, rather than hacking it into a system which was meant to support multiple human users.
Again, not disagreeing. Just saying that in aggregate, and from looking at history, the requirement of isolation in multi user systems trends towards better security.
You can absolutely build a better single user system.
