Bolt owner's manual states plugging into generator power is a no-no. Page 246:
"Do not use portable or stationary
backup generating equipment to
charge the vehicle. This may
cause damage to the vehicle's
charging system. Only charge the
vehicle from utility supplied
So much for plugging the trickle cord into a generator or an inverter, in an emergency ?
I think plugging the Bolt into a modern inverter style generator such that Honda makes would be absolutely fine. The power coming out of those is more stable than line power. The main thing GM is worried about is a fluctuation in hertz and the inverter generators take care of that with a rock solid 60hz.
Older and cheaper portable generators use a centrifugal flywheel connected to a calibrated spring to control the throttle and thus the RPM and in theory the voltage and hertz. This system works OK for light bulbs and power tools, but it's terrible for computers and electronics. The modern generators let the engine do it's thing and run in an approximate RPM and the inverter electronics regulates the voltage and hertz to amazing accuracy.