Certainly, there are plenty of exploitative bosses and we should definitely encourage people to stand up for themselves. I provide new hires with several books, one of which is a book on personal finances that includes a chapter on negotiating a higher salary. It's important to me that people are empowered in their work and their lives.
But this is not the story of the comment I was engaging with. The original comment stated:
Boss: What's stopping you from doing this every time you don't get your way?
Commenter: Nothing. That's how negotiating an employment relationship works. Holy shit.
Again for context, the original story stated that the bonus was brought up but the criteria for receiving it was never officially documented or agreed upon. The bosses decided on 30%, and the poster felt entitled for more. He's certainly entitled to feel that, and he's certainly entitled to make his case for it. He's also certainly entitled to resign if he didn't get his way.
But to threaten to resign if he didn't get it, and then resign anyway once he did get it, is just poor form. Like I said, he can do it, he did do it, the company can't and didn't claw it back after he resigned, it's now 15 years later, but this story does not portray the protagonist in a positive light for hiring again in the future.
That should not be a controversial statement. You should always know your value and worth, and this goes BOTH ways. I would say the same about any role, whether it's sales, marketing, HR, ops, customer service, or whatever else. One can't be unreliable in a company, and expect that not to be a problem for future job opportunities.