The most any normal user can say for certain about jcs getting hellbanned is, he did something annoying enough that someone did something about it!!! --Unfortunately, if you believed the previous sentence, you are mistaken.
The reality is, a lot of stuff on HN is automated. If you do bad stuff, bad things happen to you (your account) automatically. For example, if you get into a flame war and pass the "posting too fast" threshold, you could get warnings initially, and if you still don't stop, you could hellban yourself. In other words, you simply never know if a human being with moderator privileges did something, or if you did it to yourself. Also, you don't know if it's permanent or temporary.
The most I can say with real certainty is, pg is smart enough to design a system which merely gives users enough rope to hang themselves. I would do the same, and if you've studied the problem in depth, you would too. Eliminating human moderation through computerized automation is the only sane way to design a discussion forum.
Now if you were a long time, active contributor like jcs, and you ensnared yourself in the sites protective automation, and you thought someone was doing it to you, then ya, you might be miffed. You would probably react harshly, and by doing so, make matters even worse for yourself and give yourself even more "reason" to be upset.
Have you ever watched someone get absolutely livid at a chat bot?
It's hilarious. It may be a wee bit sadistic to let them keep trading increasingly heated insults with a machine, but it's still fun to watch. At the end, they might learn a valuable lesson.
With pg, there's one thing I've come to rely on; he means well. There is no requirement to agree with him on everything, but if over many years you've watched him carefully, studied the things he's said and done, or better, interacted with him, then you can be reasonably certain that he means well.
If you know anything at all about Y-Combinator, then you already know that Paul has far more important things to do than mess around with HN. If you don't know the history of HN, you're at a disadvantage; it was started as a for-fun side project to test out the ARC programming language, and HN was originally called "Startup News" for a very good reason -- to attract people with an interest in startups. The name was eventually changed to "Hacker News" due to the retrospectively obvious oversight; a lot of the best coders haven't really thought about doing a startup, and the people interested in startups are often already doing one. Broadening the scope of appeal with the name change makes sense.
If you haven't read everything Paul has written, then you don't about the massive amount of time and effort he's put into thinking about the interactions between people on (open) forums, and how to encourage beneficial exchanges between (potentially conflicting) people. HN is now, and always has been, an ongoing experiment to improve the ratio of beneficial exchanges in discussions, as well as reduce human moderation overhead. It's fun watching it evolve.
And lastly no, of the small bits of HN secret sauce I've discovered over the years, I absolutely refuse to give you the details. If the details were public, then some people would use them to game the system.