Which subreddits are you talking about? (out of curiosity, since my experience with reddit, even with smaller subreddits, is almost entirely negative)
http://www.reddit.com/r/AskCulinary/
http://www.reddit.com/r/AskHistorians/
http://www.reddit.com/r/dataisbeautiful/
http://www.reddit.com/r/DepthHub/
http://www.reddit.com/r/TrueReddit/
http://www.reddit.com/r/lectures/ (not so much the comments but more the content)