The interesting thing about Reddit, is that in a select few subreddits that are fortunate to have moderators as good as jessamyn, the experience is phenomenal and there is a concentration of domain experts sharing knowledge at a rate and depth to put even Hacker News to shame.
/r/askhistorians is one that comes to mind immediately.
In my opinion, this is one of the major reasons why MeFi is such a pleasant community compared to something like Reddit. Because the mods don't let discussions spiral out into people yelling at each other, and because drama can be dealt with on a separate subsite, it truly feels like a community of mature adults. (For the most part.)