I think you're probably right. I haven't thought about what kind of metric to look at, but it should be pretty easy to at least get close to where the interesting conversation started.

Undisciplined

If there's a high-value embedded comment lower in the subtree, it would hopefully have been zapped appropriately, though, right?  And practically speaking, it's not usually that onerous to read a subtree.  It's rare for them to cross the "see more replies" boundary, empirically.  Or at least, that's my sense.