Comment by jackowayed

He glossed over it, but this code does include URL-free posts dropping off faster. See the stuff dealing with "nourl-factor*". I don't know arc at all, but it appears that having no URL multiplies your final score by a factor of .4, meaning that it's ranked almost 3x lower than it otherwise would be. That surprises me; I've noticed that Ask HN get rated lower, but it doesn't seem that extreme.

So is Hacker News is a fork of news.arc, rather than straight news.arc? I figured it was, but never heard that officially (since people refer to news.arc as the HN "source code").

Edit: Also, the "lightweight" thing is interesting. There's something in place that sees if the post is a "rallying cry" or is mostly made of images. Additionally, if you link directly to an image file, or to some list of domains that have been deemed lightweight, that'll get marked as lightweight as well. Lightweight posts have a .3 factor, meaning that they're even more deflated than URL-free posts.