It's not powering the whole neighborhood that's the problem. With downed lines it very well might not put any significant load on the inverter yet still have a

It's not powering the whole neighborhood that's the problem. With downed lines it very well might not put any significant load on the inverter yet still have a significant amount of downed distribution lines live. Normally the fire department or the power company can just take a hot stick and within a couple minutes pull out the fuse upstream of a segment and ground out the lines making it safe from the rest of the grid. With improperly installed generators every house is a potential source of power, there's no quick and easy way to isolate all of them like their is with utility power, and grounding out every segment might not be as easy to do reliably as with utility power. If you ground out the line upstream of the fault then you know with certainty that utility power isn't going to somehow energize the portion of line being worked on but when it's being fed from more than one direction there could be a fault that isn't readily apparent that creates a dangerous situation where a linesman thinks a line is safe when it is live being powered by a generator.