However, Apple, American Airlines, Six Flags, there's been a lot of bankruptcies or near misses (Microsoft bailed Apple out in 1997) that have come back.
As far as payback goes there's historically two structures and more recently it's been a hybrid
Essentially account balances are broken up into tiers like taxes. So for instance $0-500 are paid back 100%, $500-$2,500 are paid back 90%, $2,500-$5,000 back 70% etc
It's a protective measure really. You want to piss off the fewest people and your $500,000 account holder will be pissed about only getting $200,000 or whatever but there's a huge social pressure against them to act on it because now the optics is they're a rich person stealing from the poor. So in practice it's just "grumble grumble" and you're safe from the courts
As an aside, people have been selling their Celsius accounts for a few weeks now in the same way collections people sell debt. That one is a new one. I wonder if Voyager will follow
Financial disclosure: I've got $38.00 locked up in Celsius and $10.00 in Voyager so I'm an interested but not meaningfully affected party