There’s an interesting post at the DRC forums about what could an informal D’ni script look like.
It is indeed curious that most of the things we saw written were in such a formal, tidy script, even in such places as Riven where calligraphy was surely not the first of priorities. On the other note, D’ni numbers (which derive straight from the letters, or vice versa) has something of the runic script, with the boxes, the simple curve of the 2, and the 90° angles of the rest.
So, was there indeed a simpler version of the D’ni alphabet? Yeesha’s calendar island seems to suggest so, and I would think that a D’ni housemaid would not spend an hour or two writing her shopping list in fine letterhand when she could just grab a pencil and jot it down informally; even in our highly-digital age, with printers and font faces, handwriting is still the most common (and usually fastest) form of note taking. It is true that perfect calligraphy was probably an important part of the Art (at least the way the D’ni understood it), and there are some handwritten scripts that a font face just cannot reproduce, but Writers were a very minor part of the population.