FB also has pages that post memes/pics/news/Russian propaganda, and thousands and thousands of people commenting underneath them (tragically mostly to make their friends aware of the content by mentioning their names), so that's their reddit/forums competition.
But unlike forums, most of the conversation on Facebook is 20 comments at a time and you can't just link to page X of some conversation...
I literally have no connections on FB to people I haven't met in person, and don't know a single friend's reddit account.