Maybe the answer is just to make them illegal.

Flip it around. If you are an employee partly compensated in stock, is it fair for a multi-billionaire who was one of your former bosses to flippantly trash talk the company in public after he cashes out, potentially damaging the value of your stock...? Wouldn't you want your employer to put some controls into place to prevent that kind of pointless harm to you?

You can still talk about literally anything else if you sign a non-disparagement clause or an NDA.

> You can still talk about literally anything else if you sign a non-disparagement clause or an NDA.

Why does this matter? It reminds me of the joke about how in America we value free speech so much that we can badmouth our leaders in public, but so what, in Soviet Russia they can badmouth the American leaders in public too. The question of how free your speech is, is determined by what you can't say, or can't get away with saying, without paying some hefty consequence (a punch, a fine, losing your job, imprisonment, forfeiting RSUs...).

think about it another way: it's blackmail against your employer that is actually initiated by the employer itself. you don't even have to make any threats and it's not illegal!