As many have no doubt noticed, sometimes a comment is made in a thread that sparks a tangent discussion, but it may not always warrant starting a new thread. Nested threads work well for this, but are at times hard to follow. Chronological threads are easy enough to follow until there are two or three related ideas floating around them. What if we combined the two? When replying normally it behaves like a chronological thread, but it enables and additional button "Sidebar" that triggers nested behavior allowing you to address a topic or comment that comes up, yet can be minimized (perhaps default is minimized) so as to allow the flow to continue normally.