Have u considered going in person to their office?
I seriously doubt any of their customers are able to just walk in and lodge a complaint. It's not like a stock brokerage that has walk-in locations.
Coinbase has been nuking accounts for various reasons for years now. I had one back in 2015 that got deleted due to a mistake I made (though they didn't steal my funds). And aside from making deposit mistakes like I did, they also track where your bitcoin comes from and goes to, and if there's any identifiable shady addresses they won't hesitate to make you a
former customer.
I suspect they're not doing this because they enjoy being pricks; the US government probably collects all of their customers' data and is forcing them to comply with whatever regulations exist in Coinbase's jurisdiction. So you're not alone, OP.
were your friends able to get their accounts unlocked and get their funds back?
I'm pretty sure Coinbase doesn't just steal people's money, because there's no way in hell they'd get away with that. They're not some unregulated Russian exchange operating out of a shack in Siberia (no offense to the Russians intended, of course).