I did a lot of research last year on the neutral issue - when wiring up our solar system. Also consulted my uncle who works in Wapda.
Basically, Neutral wire is grounded (into earth) at the Transformer. It does NOT go all the way back to grid. Only three Live wires come out of the Grid, so its impossible for the Grid to reverse polarity. However, as you mentioned, someone in your home could mess wiring up But then again, that's why we are supposed to use correct color-coded wires and double check all connections before powering on devices.
Also, if I recall correctly, I think the neutral and grounding issues are mostly related to Transformer based inverters. All modern inverters are transformerless so you can have common Neutral and also common Ground wire.
Btw, we also have net-metering working since past 6 months. Keeping in mind all the traditional grid issues we've had i.e. load shedding, low voltage, frequency out of range, missing phases etc, so far we've had no issue at all. At least our inverter, Infini 10KW, has a lot of protections/checks built-in and it won't even sync with the grid if there is any anomaly. Not sure about cheaper Axpert/Inverex inverters.