> almost everyone working at the company wouldn't be in the position to be able to do this

The number would have been bigger than $6.5bn.

Lockups are usually 90-180 days, and Stripe is old enough that lots of employees are fully vested. Maybe a significant number of employees wouldn't be in a position to because their growth means that most employees would've been hired relatively recently in that timeframe, but the people who were then since the early days and who have the most equity would all have been able to sell before the market turned down.

You can short sell or buy put options to protect downside in case of a crash.

Many company trading policies prohibit either of those transactions in company stock. (Some even prohibit entering into covered call transactions.) Every public company that I've worked for prohibited short selling and naked options contracts on our shares. All but one (Merrill Lynch) prohibited covered calls.

How could that be enforced, if one has some separate brokerage account (or one‘s wife).

Perhaps some hedging with similar stock is possible.

Merrill (and DEShaw before that) enforced it by forcing us to provide duplicate trade confirmations to the compliance department for all accounts held by people living at the same address. That’s fairly common in finance.

My current employer does not, so you’d only run into trouble if FINRA detected unusual profits and flagged it to the company securities counsel or the SEC made an inquiry.

My perspective is “if your company tells you they don’t want you to short shares or trade in options in the company, don’t try to find ‘one clever hack’ around the policy.”

The only exception I’d make is if you have a complete financial freedom amount of equity built up, at which point, I’d consider quitting the company, and only then entering into such a hedging transaction outside of a blackout window (and when you had no material, non-public information). That would likely pass any “valid purpose” tests and be considered clean by regulators. (It’s not really the company I’d worry about; they can only fire you and whistleblow on you. It’s the regulators that I’d worry about. The company policy is designed to protect them, but also help keep you out of the grey areas as well.)

Also see 12-15 in section III here: https://www.finra.org/rules-guidance/notices/19-18

There is a lot of automated review (post-trade) to find and flag possibly suspicious activity. I think the FINRA team spoke at one of the Re:invent sessions (maybe even in a keynote?) about how they detect possibly anomalous trades for manual review.

As sibling says, company trading policies usually prohibit shorting the company stock. Also, you have to exit any options during blackout windows. So: not really.