Today, I ran into a very cool Thunderbird plugin, via David Ascher : ThreadVis
I remember having read the original IBM paper on this idea by Bernard J. Kerr
a while ago, and it was a very interesting take on thread visualization. I remember thinking at the time, bummer, I wish there was a Thunderbird plugin for this. Well, it took a little while, but it's finally here.
The idea is to use arcs to represent the relationship between the components of the thread. Why are most email threads displayed as trees, I am not sure. Looking at actual threads in my inbox with this addon confirmed to me that the idea has some merit. I especially love the fact that in this implementation, the arc length is relative to the time between 2 replies.
It's part of it's author's Master Thesis, so the extension also includes anonymized usage data extraction, to help him analyze how this is working out. It's optional, disabled by default, but do trun it on to help him out (I did).
If interested, install it directly from the official Mozilla Add-Ons site.