While it is true that the mount is the ground return, it’s nothing to get paranoid about. The high spark voltage has no problem jumping across any resistance.
Like Frank says, this should not be an issue for the several thousand volts finding their way back to the coil.
But, there is a ground wire on the little 2hp that is very important due to the plastic bushing on the mag plate that insulates the high voltage return. There is a ground wire on everyone’s favorite “low tension system” as well. On this engine, it is the primary lower voltage that returns to the mag plate.
Those are good reminders at a good time. Thanks, Don!
Long live American manufacturing!