OP is the author. When an author submits the item to HN it is common to do like here, writing a HN specific title for the submission that is different from the title on the page itself.
It's true that when it's clear that the submitter is the author, we often leave their preferred title in place.
But the submitted title in this case ("Every person should come with a user manual. So I created one for me.") was baity and therefore against the site guidelines, so we reverted it the way we normally do.
But the submitted title in this case ("Every person should come with a user manual. So I created one for me.") was baity and therefore against the site guidelines, so we reverted it the way we normally do.
https://news.ycombinator.com/newsguidelines.html