I think reddit is the reinvention of USENET. It is mod-heavy and has enough critical mass of users to provide excellent results from its upvoting system. And many subreddits are extremely well maintained with a very high signal to noise ratio.
It even has its equivalent of alt.binaries.pics.* if one is so inclined.
Sort of, voting rearranging the chronological stream of conversation makes it significantly different IMO. There is also the phenomenon of funniest image tending to win the votes, too. (Barring excellent moderation, but Reddit does very little to make moderation easy, or even set goals for moderation.)
That's not great for discussion, but then Reddit was always designed as more of a system of briefly commenting on URLs than actual discussion.
This is only true for the front page and for things like /r/AdviceAnimals. The front page is in and of itself a separate phenomenon than the rest of the subreddits, in my opinion.
For many subreddits, there are truly fantastic discussions that are very relevant to the subreddit topic. /r/askHistorians or /r/askScience, for example, has an extremely high signal to noise ratio.
It even has its equivalent of alt.binaries.pics.* if one is so inclined.