I don’t understand why such a big deal is made of whether people can “keep their insurance coverage” or not. Who cares?
As long as my coverage is good and it's not a hassle to use it, what difference does it make who provides it? I've had my same insurer for years now, and if I got a new one tomorrow with the same premiums and benefits, I wouldn't spend a minute more thinking about it.
If Medicare for All provides equivalent benefits and I'll pay less overall, then I'm all for it. Plus, it removes the profits of the insurance industry from the costs.