I'm not sure we can hold individuals responsible for signing these non-disparagement clauses. They often don't have a lawyer to review the paperwork and, I am sure, employers like Facebook aren't going to wait for a new hire to have a lawyer review that paperwork. There's a real pressure to sign everything with HR and get on to starting your new role.

Plus the power imbalance.

In this case the author is an attorney, so can presumably understand a contract she signed.

And the non-disparagement wasnt in her hire agreement, it was in her severance agreement, in exchange for a negotiated amount of money. Author was wealthy enough to afford dedicated lawyers to review.

If you can't hold individuals responsible for signing contracts on the premise that they might not read them, you've simultaneously invalidated most contracts, increased the cost to enter a contract (essentially subsidizing the law industry), and severely limited the ability for individuals to enter into contracts — not to mention infantilizing adults who are fully capable of reading a document before signing it.

Furthermore, this was a severance agreement, not employment agreement, so having a lawyer review your contract is not going to delay you from starting your role.

I have my issues with this situation, but "they might not have read/understood the contract" isn't one of them.