HN does various title mangling: capitalising things, removing words like “your” and numbers from the start, that kind of thing. I strongly dislike it because it harms titles far too often. Fortunately it allows you to second-guess it by going back and editing the title after submission.
It desensationalises/de-clickbaitises/de-Buzzfeedises a lot of stuff. The submitter can edit it, and the edit doesn't go through the same sanitisation. Also if it's popular enough for a moderator to notice/they happen to, they often fix them too (or sanitise further in other cases).
I imagine that it looks more reasonable when you see all the submitted titles; there may be many that it improves—I don’t know. (I still think it should be reviewed and probably curbed or discarded, but I’m confident that there’s a reason it’s there; dang knows that it regularly does harm to titles.)
