Did you know that, despite the sinister (pun fully intended) associations of left hands, some scribes were actually left-handed? Paleographers know this because unlike right-handed scribes, for whom writing involved pulling the pen and ink across the writing surface, writers who held the pen in their left hands would have had to push the ink over the surface. This forced them to completely change their ductus, or the way in which they execute strokes. This according to Malcolm Parkes, in Their Hands Before Our Eyes: A Closer Look at Scribes.
Parkes also explains that handwriting can be used to determine how many words at a time copyists held in memory while turning their attention from the exemplar to their sheet, since words held in memory together tend to be aligned vertically, while stopping the motion and turning the gaze to the exemplar causes a break in the aligment.