Reddit has a pretty straightforward structure. It's basically a discussion forum where people post links or questions, and other people reply to them. I like working with it because the replies are well structured (people reply to specific comments, rather than just posting another comment on the same thread), and you can get very deep reply chain. Each comment has a general topic, a thread title, an author, and of course the comment body. There's nothing particularly special about the discourse structure; it's just a very large and active source of discussion on a variety of subjects.