I remember in Usenet there was often a competition how much you expand a thread sideways. This might the optimal format. A discussion board with only one thread branching infinite. You could then search for significant node points, which have created more discussion and node points. Now to avoid endless wallowing in same shit year after year, I suggest automatic AI system, which does not cancel anything, but moves an arcticle to the node it mostly belongs. And as high as possible regardless of creation time.