Which eight from this group looks the most balanced? Most people whose eyes have been trained by long exposure to the conventions of the Western alphabet would probably choose the third from the right, or even the second from the right. But the third from the left is the one where the two component circles are the same size. To most people this 8 looks top-heavy because we expect the bottom element to be larger.
This is just one of the interesting typographic design considerations detailed at briem.ismennt.is, apparently an Icelandic typography site, which is oriented to type designers. (The site’s one frustration is that it gives little information about its author, apart from the facts that “in 1996, [he or she] taught a short type design course at the Royal Academy of Fine Arts in Copenhagen,” and that an Icelandic version is offered.)