Interesting article! It's a shame the documentation is lacking :(
Oh, and as for the different sorting options:
- Hot sorts by the number of upvotes and how recent the post itself is
- Active sorts by number of upvotes and how many recent comments a post has (lively discussion ranks higher)
- Scaled sorts like Hot, but tries to prioritize or give more weight to smaller communities
- Controversial sorts by giving comments or posts a higher rank if they have an even mix of down votes and upvotes