The deep relations (7-table join) example in the link is something I wouldn't do (including the repeated 'user' entities) with an RDBMS, given that I expect some elements of some tables to appear multiple times, that's a waste of I/O and hard to cache.

> Users have friends, friends have posts, posts have comments and likes, each comment has one commenter and each like has one liker.

I would likely gather all the instances of User id in each context (user, friend, commenter, and liker) and query it separately from the JOIN query. Depends on your data which way works out better on average/worst-cases.