Someone told me the other day that if a non-resident drives your CH car in Switzerland and gets into an accident then your insurance will not cover it.
I know it can be problematic if your German friend drives your CH car into Germany (they may view it as he is "importing" the car) but driving in Switzerland?
I am planning a motorcycle trip to Italy later this summer, and my American friend will be driving my CH bike (I can borrow another bike). Now I am worried he is not insured (he also has a personal US motorcycle insurance).
I'm pretty sure the same rule applie as you note about driving a CH vehicle in Germany. You can ride your CH bike in Italy. Your American friend may not. Only you (or another Swiss resident) may ride your CH bike outside of Switzerland.
If the American friend is not an EU resident, then there is no issue at all (at least from customs point of view). Only EU resident cannot simply drive/ride non-EU vehicle in the EU customs area.
Yes, if they have a valid driving license, the car is roadworthy, they are not intoxicated or their driving ability is not otherwise impaired which would make them unfit to drive.
Normally also yes as the insurance covers any driver. Or as others say: The car itself is insured. (There might be some special insurance where only one named driver is insured, but they are rare).
Further, the customs issue mentioned should not affect the insurance coverage at all, as driving is not forbidden by the traffic law, but customs regulations.
The issue in this case is about the illegal importation of a motor vehicle and nothing to do with licensing or insurance. Residents are entitled to drive their car across EU borders for the purpose of everyday living, provide the car is owned by them or at least someone in the household. Beyond that rule of thumb there are various complex rules and regulations.
It's even more complex in the case of the UK, where UK citizens resident in NI and Irish residents can drive back and forth over the NI border, but can't continue on to mainland UK from there..... Prior to BREXIT, there was a very big business in the UK selling cars to people in the Republic. British dealers advertised in Ireland and Irish people flew over, bought a car and drove it back without an import duties or taxes....