I think all of these are natural and healthy parts of the human growth, and legitimate uses of online conversation. Not everyone else feels this way, or care about the context of speech they find objectionable.
But to the degree that HN is "privacy hostile" as you put it, with regards to not being able to delete comments, I'd say that it's also "privacy friendly" to an almost equal degree, given there is absolutely no personal information required in order to create an account.
And there is none of the usual invasive social network crap which drives me away from literally every online platform apart from HN.
If anyone has an issue like this, you're welcome to email hn@ycombinator.com and we'll see what we can do.
Between "how deleted are my comments, really?" issues, and the number of sites that get hacked in a given week - I would not trust anybody's supposed "delete" feature for anything important.
(And for critical stuff...you might be able to talk @dang into performing a Sword, +Admin deletion here.)
On reddit this is a right pain, and really fragments discussions. Ending up in a 7 year old discussion with half the comments [deleted] or "I've overwritten all my comments with this bot" is not brilliant. Doubly so when you're trying to find a solution for a technical problem.
As to your second point, reddit is not a public archive, or a court room, or any sort of entity that I would trust or expect to retain, much less make accessible, "public" discussions, technical or not. They have no obligation to give you anything, and the moment it's profitable for them to switch to pay-to-play, you can bet they will. Steve Huffman, the CEO of reddit, killed all the 3rd party apps accessing reddit, no? Not someone I will place my trust in.
[edit- added the below]
I would also add the court of public opinion is a place no one should be tried, and peoples' privacy trumps your desire for information, so it makes perfect sense that comments would be removed or stripped of a byline. Adding a byline redaction feature would be cool imo.
It's been a few years since I read the GDPR, and I'd have to re-read it again with HN's use case in mind, but I'm reasonably (though not completely) sure that "delete every comment you ever made" isn't covered.
Some people reported it found their old/alt accounts.