Don't confuse "edit" with "editorialize". Editorializing is editing a title to put one's own spin on it.
HN's actual rule isn't hard to find—it's in https://news.ycombinator.com/newsguidelines.html, which is linked at the bottom of every page and which commenters here ought to be familiar with. This is what it says: "Please use the original title, unless it is misleading or linkbait; don't editorialize."
Note that "unless".