Tim, I think better tracking would be really useful.
First, it sounds like you have already found the Reports for a course on the Navigation tree?
Second, the Moodle Participation Forum (a contributed plugin) works with Brant Knutzen's Participation Map to give you a technicolour visual representation of those threads of interaction. Worth a look.
Third, there's an interesting example to examine in Instructure Canvas, which seems to provide better analytics out-of-the-box than Moodle at present, and more flexibility around "conversations" (ad hoc, selected people, versus planned whole-class forums).
If anyone is doing what you describe, I know instructors who want it!