I have a friend who works for the UK grid. He visibly winced when I mentioned the plug in back feeding systems a while back. They’ve had a few close calls with “off grid” setups being used on grid.

Apparently even properly installed solar is a serious problem, though that’s more down to the sudden demand shifts it creates. It throws off their predictions and threatens grid stability at times.

I’m a big fan of solar, at all scales, btw. We just need to remember that the grid is not just a dumb system, it has a lot of active parts that were never designed or intended for use with microgeneration.