Earlier quoted context omitted.
But signing something without not understanding it is too naive. So, assume I already left the company and exercised a big bag of common options and so I have a decent amount of common shares. If they tell me to sign something that looks shady I just say: "No, it looks shady". What then, can they do?
Threaten to shut down the company. Then your shares are worth zero.
I am not naive enough to believe it would work, as they would probably find a way to screw me regardless, but my stance would be firm.
After my experience with startups I have become completely intolerant to corporate greed and injustice, so these days I am purely in a business transaction with my employer and I know exactly what to expect and when to expect it (which is why I get paid in RSUs rather than stock options). I like to think I wouldn't fall prey to this sort of petty begging.