hackernews is very upfront that they do not really care about deletion requests or anything of that sort, so, the opt out is to not use hackernews.

By posting comments on this site, you are relinquishing your right to that content. It belongs to YC and it is theirs to enforce, not yours. https://www.ycombinator.com/legal/

The back button

Create a new account every so often, don’t leave any identifying information, occasionally switch up the way you spell words (British/US English), and alternate using different slang words and shorthand.