But HN's ethos is to inspire discussion and readability of it. Lack of a delete seems to be by design so that conversations are always readable.
You can see the spirit of that in their guidelines[0] such as "Comments should get more thoughtful and substantive, not less, as a topic gets more divisive".
You can further see that in the design in how they handle deletes [1], where once "archived" things are permanent
[0] https://news.ycombinator.com/newsguidelines.html
[1] https://github.com/minimaxir/hacker-news-undocumented#editde...