Just adding my advocacy for a delete option. Hacker news has been around for long enough, it’s only reasonable that you give the content creators control over that content. Did i even sign a TOS back then?
The problem is that the content is a co-creation. Comments aren't atoms, they're nodes in a tree that only make sense in connection with other comments. A reasonable deletion policy needs to fit this domain, and that makes it more complicated than "these are my posts and I'm taking them back and going home". It's not that we don't care about users or don't want to treat them fairly; not at all, and we go to great lengths to help.
While I agree that it breaks the conversation around others posts by allowing deletion, at the end of the day this isn't unique to HN. If i delete myself on Facebook, i delete myself, why does HN feel it's special in that it deserves to maintain conversation integrity?