If someone emails "I was younger and wrote some stuff I'd love to get rid of", the obvious response is: "Happy to help! What are the links? We may not be able to delete the posts altogether (it depends on whether they got replies, and how many) but there's nearly always something we can do, and we don't want anyone to get in trouble from anything they posted to HN." I've written that kind of thing so many times I'll probably start mumbling it in my sleep soon.
I would have to go back to my inbox to find your response but I remember being pretty disappointed. I don't think you wrote anything that was specifically unkind but I remember being struck by the response. I thought "wow, these guys really don't care if someone wants to delete or hide their account." It is completely possible I caught you on a bad day.
I'll try again.
Just found out the edit option disappear after a few minutes/hours on HN
Now I'm really bothered too, about the lack of a delete button.
It's important for the coherence of HN threads that discussions proceed in a mostly-append-only way, and that the history be sort of 'committed' or 'trusted' after a while. That doesn't mean that nothing can change, just that at a certain point, changes need to go through a manual process, as I've explained in other comments in this thread.