The exceptions are spammers and serial trolls. For those we continue to use shadowbanning, for different reasons. In the case of spammers, telling them they're banned would just invite more spam, and in the case of serial trolls, would invite more trolling—besides which, serial trolls know perfectly well that they're banned. That's what "serial troll" means. The account you thought you were helping by telling them they were banned is one of the latter, and if you saw the shockingly abusive things they'd posted in the past I'm pretty sure you would think twice before casting them as an innocent victim.
Don't you think it would be fair to update your views after 8 years? HN moderation has changed massively since then. When pg was the sole moderator of HN, it was impossible for him to put the kind of attention into moderation that we've been doing since we took over in 2014. That's the primary difference.
If you look through my comment history you'll see that I've posted tens of thousands of comments and spent thousands of hours exhorting users to follow HN's rules, cajoling them and coaxing them and warning and scolding and coaching and helping and teaching. We cut people an incredible amount of slack before banning them. It's repetitive work and frequently meets with aggressive attacks and imaginary accusations. I think it's reasonable to expect a decade-long user like yourself to cut us a little slack too. If you think that we're beheading people without consideration, or treating them in any way disrespectfully, let alone unethically, I would invite you to observe more closely. I slip up sometimes and am happy to make corrections when people point that out, but I don't think charges of systemic malpractice are justified.
I know it takes a lot to sit down and write out a response like this over and above the work you put in to making the site a usable venue. Doing so makes a difference.
I'm not trying to bring you down. I really am talking in good faith. And I know agitators can wear you down. Perhaps I haven't come to terms with the needs to isolate or sandbox people online. Perhaps I didn't read his history, but I tend to give HN accounts the benefit of the doubt more than most.
Anyway. No worries. I hear you.
Note my name. I was shadow-banned for one sarcastic comment eight years ago, despite being an otherwise good-faith, decent contributor. Maybe things are different now, but I've never gotten over the feeling of wasting my time putting thoughts together and responding to a conversation and finding out I muted.
Hell, I'm a mod of a city subreddit, and one of the other mods has shadowbanned a complete asshat of a person. I don't have ban powers, otherwise I would ban them outright. It makes me uncomfortable to be a party to disrespect like that.