All of the scenarios described by you may unfold. That's why I'm interested in a debate first, to try to see as many "holes" in this construction as we can.
I think that if we make this optional, we will be able to track trends better. We may see which authors are "colluding" with other authors. It will probably segment the conversation leading to more vertical conversations (more root posts compared with comments).
And if it's optional, people can reverse back to it at any time.