The reason you don't joke about firing someone is because of the power imbalance. The employee will usually be in a bad spot if they actually are fired, and the company will be fine (usually better off, even). Furthermore, there's no real recourse on the employee side. If they are offended by the joke they can't really complain, because if the boss is so tone deaf as to joke about firing, they're unlikely to take criticism like that well.
No such power imbalance exists with an employee joking about quitting, but I also struggle to think of any situation in which it's actually a funny joke to make.
>The employee will usually be in a bad spot if they actually are fired, and the company will be fine (usually better off, even).
Boss, to employee: "I'd just like you to know that I'd never joke about firing you. I recognise that it would be needlessly cruel because, although you're reliant on the company to earn a living, the company would actually be better off without you." D:
If the company is firing someone it's [probably] because they're in a better position without them. I probably could have phrased it better but it's somewhat tautological so I didn't think it would be that offensive of a statement :)
No such power imbalance exists with an employee joking about quitting, but I also struggle to think of any situation in which it's actually a funny joke to make.