Awesome data. Really interesting to look at, and great presentation.

But there are a few things that kinda bother me with this:

The problem I can find with this data is that it isn't a representation of the reddit hidden communities as a whole, just the hidden communities of those who actually post (only 20% of Reddit).

A question I have is whether these are two-way connections with the groups. It's not clear exactly how the analysis is done 100% (perhaps I missed this portion), but could connections between subreddits be generated by there being a lot of people who post in a very tiny subreddit also posting in a larger subreddit? This means that though someone may like Large Subreddit A, they may not like the more specific Subreddit B. But a lot who like Subreddit B like Subreddit A.