What you say is all true, but there's one thing that probably hasn't hit most HN readers yet: the job-hopping stigma. It sucks that it exists, but it can catch up with people after a certain point.
Yes, good programmers can generally get better jobs quickly, but there is a point some people get to where the "job hopper" image starts to hurt them. Most people, if they see a string of 6-month jobs, assume this person is constantly getting fired.
On the one hand, if you are in need of work (maybe you quit to do a startup and then your startup failed) and you do you have a resume that is starting to throw the "job hopper" flag, it might be time to ask yourself why you're even applying for another company and if you'd be better off reinventing yourself as a freelance consultant instead.
On the other hand, "Because I'm broke and need a paycheck right now" is probably the most common answer, and those are exactly the people who get bit by this stigma. Because no company wants to permanently hire someone who is only applying out of temporary financial need.
I think that as a society we need to create the political and economic conditions necessary to make freelance consulting a more viable career path for skilled individuals. There are a lot of obstacles and frictions that could be reduced.
I don't think employeers worry these people got fired. I think companies are concerned whether you're just a hired gun (not that there's anything wrong with that). But if I'm a young company and I want someone to come on board, I'm not making the decision lightly. I want a long-term partner. So yes, a lot of short term employment would be concerning.
At 6 months, literally "fired" is unlikely because most companies don't act fast enough. But the assumption people make based on a lot of short job tenures is that the person was unsuccessful at all of them. Most unsuccessful people don't stick around long enough to get fired, but that's irrelevant.
It's somewhat self-reinforcing, I'd imagine. Because of the stigma, people are less inclined to leave jobs, and therefore a higher percentage of departures are negative.
There's also a "can't win" dynamic from short job tenures. If you're obviously moving up, you're a mercenary. If you have a lot of lateral moves, you're unsuccessful.
Additionally, I think few people actually want to be job hoppers. I'd love to find a 10-year fit. On the other hand, it's uncommon that a I find an environment where I keep learning for long enough to justify more than a year or two.
You aren't likely to go back to your previous job, but even a failed startup should qualify you for a better job.
If you have the oppertunity, go for it. You regret the things you didn't do more than the things you did do.