Home inspectors have nothing to do with enforcement. The NEC never allowed grounds and neutrals to be connected in a sub panel in the same building. In addition to what Marc said, I'd mention the improper jumper between the main lugs at the sub panel and the problems with an upside down breaker in the FPE panel. The green wire at the main lug is a giveaway that this entire installation is not to be trusted. You might want to do some research to find out when a 4 wire feed for a sub panel was actually adopted by the NEC.The 3 wire feed was accepted for many years before the change was made. Youre right home inspectors have nothing to do with enforcement,Suggesting that something that may not of been a code violation at the time of install is very tough to convince a home owner to repair/change. Thats like saying every house you inspect should be gfi or afci protected whether or not it was code when the house was built,or the last time it was remodeled.