@devnull @david_megginson @davew @evan its when the neat, sequentially linked comments become a bushy tree if somebody replies to a comment higher up.
A busy "discussion" (that may last days or weeks) with many participants in different branches of the tree is very cumbersome to get an overview of. Like parallel, non-interacting universes.
Not to mention that every new joiner in the discussion reduces your available reply text length, but maybe that is a feature not a bug :-)