Ask HN Mods: Why Do You Completely Change What Users Submit?
I asked a very similar question of dang [1] about two months ago when he decided to change an article's URL to one I added to the comments [2].His response to me (w/ irrelevant stuff redacted):    The short answer is that HN's goal is quality, so that's
    what we optimize for. Optimizing means trading other things
    away. One thing we're willing to trade away–if it's a clear
    win for quality–is fidelity to the original submission. HN's
    focus should always be on the content, and the details of the
    original submission are of little interest compared to the
    subject at hand.
    
    HN isn't a purist's kind of place. Our goal to make the
    front page and the threads as interesting and substantive
    as possible. We change a lot of things to serve that
    principle. If we knew how to serve it better, we'd happily
    break more crockery to do so.
    
    Someone (perhaps a purist!) will object that terms like
    "quality", "interesting", and "substantive" have no precise
    definitions and are in the eye of the beholder. True, but (a)
    they're not arbitrary either, (b) the alternatives suck, and
    (c) someone has to make the calls. We don't get them all right,
    but we do try hard to correct mistakes, and I'll defend the
    principle any day.

1: dang = Daniel Gackle, HN's moderator. http://blog.ycombinator.com/meet-the-people-taking-over-hack...2: Original thread: https://news.ycombinator.com/item?id=7747401