I feel badly for you that you've been at jobs that have made you feel that way. I've worked 50ish hours for a long time, generally in jobs I enjoy and in compensation structures that rewarded me for do intellectually stimulating work.
But 50 hours a week is hardly crazy. Do whatever works for you, but I want to combat this strange myth that nobody can be productive after 35 hours a week. It's obviously false from my experience (and I would guess the experience of many, many people on HN).
Not at my current employment, but I know there have been jobs where, say, 3:30 would roll around and my brain would pretty much fried for the day, but I felt obligated to stick around for an extra hour and a half because I'd get disapproving stares if I peaced out early. That extra hour and a half the company got of my time as not a useful hour and a half though. Or conversely sometimes I'd stay late because I was engaged with some sort of problem. Either way, the number of hours really had very little to do with my productivity, and trying to "force" it was never particularly useful.
If I were a manager, and I saw a person was treading water, I'd rather them go home and have them come back the next day refreshed, rather then have them stick around being miserable to meet some arbitrary number of hours.
Some of the people I've seen who can do 50 hours of productive work are in roles that extend beyond programming where there is a good mix of things.
That said there is a limit too.
Working beyond 40 hours is non-productive is a rhetoric I see often on Hacker news. And it always blows my mind. My life experience has been exactly the opposite.
The parent article does not state it as a requirement - more so as a nature of reality for the more ambitious folks in the startup vs. corporate category. I find exceptional folks in my company to be also very hard workers - by choice and not by force. And there are plenty who live a precise 40 hour schedule. Which is fine for both parties as long as that's what they want. What I find pretty ridiculous is the very common new-agey declaration that there is only one right way for everyone which is "40 hours of work" and anything else is just a waste of time. I think it is a very appealing life-style for many - but not a reality for many people who want to get ahead in their careers, are ambitious or are attached to the nature of their work. I see nothing wrong with that.
This may be a "dangerous" thing to suggest, since I realize it edges on a "if no one does exceptional work we all look fine" mentality which certainly isn't productive, I just mean to stress that buying into 40< hours may have ripples in terms of legitimizing it as a Carte Blanche system, (Yes, this is a slippery slope argument, but having seen it pan out as I've described I'm less hesitant to lend it credence.) and as you say, an appealing life-style for many, or some, certainly might not be for all.
I'm not against doing some extra time if needed, but working overtime regularly with the 'I like my work' mentality is for me the wrong way of thinking, since anything you could be doing sitting at a desk for your employer outside the agreed hours you could be doing it for yourself.
I've worked in one startup, another one on the process of becoming a small corp (i.e., already adopting process in a much serious scale) and a corp. The best by far, if you value your life outside the job, is the corp. The worst was IMHO the second one, which had the worst of the two worlds: from the startup world, disapproval stares whenever you left without doing enough overtime, crazy schedules overall (I learned later that some mandatory things were actually illegal in my country) and permanent fire-extinguish mode; from the corp world, bureaucracy and lots of meetings. This was in Europe, not in the US.