I find that as soon as you introduce threads as a form of organization, you've already lost the plot with 75% of users.
One may argue that Facebook has threads, but I don't actually think people know how to use them. They simply click reply, say their piece, and then it's lost forever. They have no concept of structure.
I don't think Facebook knows how to use them, as it typically hides most of the comments under a thread and picks out a couple irrelevant ones without their context.
I suspect that's intentional and they're using them to show things you'd likely reply to... and then just bury the rest. More of an opinion black hole than a discussion system.
One may argue that Facebook has threads, but I don't actually think people know how to use them. They simply click reply, say their piece, and then it's lost forever. They have no concept of structure.