I'm not the newest user here, but this is what I think on that specific subject....

Every time I think about comparing HN to Reddit, I am jarred back to reality by comments that start with "I work in [extremely specific field relevant to article]" or "I did [X project] with [Y person at center of discussion]." People show a different face depending on the group culture, and HN just draws a different humor out of people than Reddit does. The same person could be very serious on HN, and then turn around and write looney jokes on Reddit.

There are certain areas of Reddit that are informative and moderated to maintain a high degree of quality. I think they often deal with a shared hobby, profession, or pursuit.

Reddit has been ruining HN every year since 2007. You'll find links to comments to that effect in the last item under Guidelines in the site footer:

unalone on Nov 6, 2009 in "Ask HN: Is it just me, or are HN comments becoming..."

I'm at a year and a half. Hacker News is turning into Reddit. It's following the exact same path, albeit thankfully slower, and the causes behind that path—influx of users, need for attention, karma lust—aren't causes that Paul is looking to fix.

Reddit's not the worst thing in the world, but make no mistake, we're headed there.

The earliest linked:

_csoo on Apr 17, 2007 - Since when is Startup News synonymous with reddit?

That Guideline with the links suggests "Please don't post comments saying that HN is turning into Reddit. It's a semi-noob illusion, as old as the hills."

Yes, this definitely contributes. You see these changes in the language used and in the voting habits as well.