I know it because it's in the spec necessary for licensing. It shuts off in under 20 ms so you can't even get shocked by the prongs of the plug if pulled out.

Utilities must approve power export to the grid, even if you do the physical installation 100% off the books. It's called “Permission to Operate”, which requires permits and passed inspections. You can’t just unilaterally add shit to the power grid.

https://www.energysage.com/solar/solar-interconnection-what-you-need-to-know/

The PRODUCT is designed to stop feeding OUT the plug if it doesn't detect CURRENT from the socket. AC is alternating current so it pulses on and off so the solar system is doing the same. It's turning on and off quickly and seeing if it gets power back and if it detects no power incoming it shuts off the power from the solar. It's quite simple and ingenious.

Too high, too low, or out of frequency range.

The same thing that currently happens when somebody does that with a gas generator? Linepersons get zapped… people get sued… etc…

There isn’t any data transmission over the wires…

That’s very wrong. Not only can you extend Ethernet in your own home using your power outlets, the power companies have been reading meters this way for decades.

I agree with everything you said except shoe-in, because it's shoo-in.

But you articulated (better than I was going to) the number one issue. Power companies need insurance and their insurance will be affected if ordinance permits basically unchecked generators being plugged into the grid. And before anyone says it, you are not allowed to just plug your generator into your house. Does it happen? Yeah, people have been dumb since day one.

But there are transfer switches that allow for this operation in a safe manner, and the easiest way to deal with this is to have them installed by default in new construction, and to provide incentive for upgrading your panel to include one.

Many inverters aren't even UL listed.

Yes but many inspectors and insurance companies won't want you to install electrical equipment on "real property" or buildings if it isn't UL as that falls into the scope of AHJs and insurance providers. If there's something that has the potential to start a fire, you need to have safety certifications so operating the system not only reduces the risk of fire, but also selling the house in the future to a new owner doesn't come with excess burden on behalf of the next insurer.

If your solar system is off-grid AND off-building, I see no reason that you need to have a UL listed system.

This is of course dependent on local AHJs and utilities, but UL 1741 covers both standalone (off-grid) and grid-interactive (on-grid) inverters. If you're choosing an inverter manufacturer that makes non-UL listed off-grid inverters, I would probably be suspect of their products' quality as it's easier to gain UL listing regardless of how the inverter is used: off-grid or grid-interactive.

That's the problem.

That is a problem. Off-grid inverters that aren't certified to UL 1741-SB aren't required to have anti-islanding protection that cuts the inverters off if there's an absence of grid voltage. If a "balcony solar" inverter were to NOT cease to energize upon loss of grid and stay islanded, then voltage is introduced to the building's/community's shared local distribution system. If work were to be done on that portion of the distribution system or grid where lineman and wireman expect conductors to be de-energized, then you might have injuries as a result. Now, you may be able to say that lineman and wireman should always test for presence of voltage prior to doing work, and as a solar engineer I would absolutely expect folks to do this, but that's not always the case. People cut corners. And in the event that certain crews cut corners, don't check for voltage and investigate where the voltage source is, and start touching wires and introducing paths to ground, people can get seriously injured or die.

You may think that because solar panels are current-limited that this fact protects workers in the event of becoming exposed to live voltage, but any combination of voltage and current can kill.

I've always wanted DRM for my inverter.

In the context of safety, this is a good thing. Skirting DRM on movies or TVs won't mean you injure yourself or others or worse. Skirting inverter settings can cause inverters to operate in ways that are unintended, and could hurt people. These things are not the same, and it's concerning that you can't see the difference.

Also, having locks on settings means that other bad actors are deterred from changing those settings maliciously, whether intentional or not.

There is not substitute for a qualified person operating and maintaining an electrical system, regardless of voltage.

I think it should just require a permit

Agreed