Version: (using KDE 4.4.0) OS: Linux Installed from: Fedora RPMs Emails reporting additional comments to a bug report do not carry a header that allows threading. With the advent of automatic bug reporting tools causing many 'duplicate' reports, threading would make it so much simpler to follow and pick out which reports to open and read thoroughly.
They do (now?). Followup comments emails do have the In-Reply-To header.