No, an inverter (at least the small consumer models) has no connection to the ground pin. On a PC it will be hovering around 60v above and below the neutral and hot because of the noise filter in the PS.
I ran a jumper directly from the PC power supply can to the car frame to fix the hum. That made DC ground in the PC the same as ground in the car. Prior to that the ground connection was through the shield of audio signal cable (which is also a signal path).
As for IG, it seemed like a good idea but IBM abandoned the recommendation in the late 70s as being a waste of money.
Most of the noise was coming from our switch mode power supplies in the first place. They fixed the PS problems and the noise problem pretty much went away. The use of CMOS instead of TTL also made machines a lot more noise tolerant. They also lost their obsession with "ground loops" about that time and we stopped doing all the base plate ground checks insuring the holy grail of a single point ground. For the last 30 years multiple grounding points in computers became the norm, using the logic that creating a ground plane was better than striving to have "star wired grounds". Look at a PC interface sometime. Every one of those D shell connectors grounds through the shield of the cable. When we had transient problems we added bonding, which by definition is a ground loop. Just like 250.6 says, we did try to avoid signals on or referenced to, the ground tho. That is why you see so many differential interfaces like Ethernet, Twinax or Token Ring. The newer machines even went to a differential SCSI interface.
It is duly noted that the only damage I have ever seen on my PC was a lightning hit to the weather station mast and it broke a single ended serial port interface.
Unfortunately old legends die hard and I still here about ground loops, IG circuits and other things that went out about the time we threw away our bell bottoms and leisure suits.
