During the VA301 course in Sabanci University, Elif Ayiter pointed out the repetition of script typefaces and ow that repetition defeats the purpose of the whole handwriting imitation of such fonts. This got me thinking:
As script typefaces are becoming less and less commonly used and certain script typefaces become avoided completely, I try and explain why this might be happening by using Mashahiro Mori's The Uncanny Valley hyphothesis about human-like robots as a framework for discussion.
The Uncanny Valley
The Uncanny Valley (1970) hypothesis of Mashahiro Mori takes Freud's theory of the Uncanny as a basis. Freud's 1919 essay The Uncanny focuses on the qualities that make some subjects in literature appear as unheimlich (un-homely), uncanny. Mori builds on the essay of Freud and argues that robots acting and appearing as humans breed the feeling of eerieness in humans and draws up a “valley”, describing when and in what levels the uncanny qualities of human-like robots emerge.
Charles Darwin, in his book commonly known as Voyage of the Beagle, describes the uncanny quality of a snake and explains the hideousness in terms of snake's face's proportions being in relation to a human's face.
The expression of this [Trigonocephalus] snake’s face was hideous and fierce; the pupil consisted of a vertical slit in a mottled and coppery iris; the jaws were broad at the base, and the nose terminated in a triangular projection. I do not think I ever saw anything more ugly, excepting, perhaps, some of the vampire bats. I imagine this repulsive aspect originates from the features being placed in positions, with respect to each other, somewhat proportional to the human face; and thus we obtain a scale of hideousness.
—Charles Darwin, The Voyage of the Beagle[34]
Script Typefaces and Repetition of Organic Forms
The first script typeface cut in 1557 by Robert Granjon in France and was named lettre françoise d’art de main but was widely known as Civilité because of it's use in a popular children's etiquette book La Civité puerile.(Tova Robinowitz – Exploring Type, p147).
Casual script typefaces such as Comic Sans, Brush Script and Chalkboard mimmick casual human handwriting. Because of the nature of rendering of the glyphs as single units, in long bodies of texts, the pattern is instantly noticable in repeating glyphs which defeats the whole purpose of mimmicking organic flow. Instead of looking organic, they now look as if they were robots, acting too hard to move like humans do.

Even in short texts, the repetition becomes clear quickly

Loren Ipsum in Comic Sans
It is clear that because of the mechanic rendering of such typefaces, the resulting text does not appear as human as it was intented to be. I argue that there is an uncanny quality to the downfall of such typefaces basing my argument on Mori's The Uncanny Valley hypothesis. To remedy such eerie results, such fonts can be scripted to have alternative glyphs that are randomly picked by the software while typing to replace the choosen glyph with a similar copy in real-time. This would aid in blurring the clear repetition of glyphs. Furthermore, some glyphs can have stroke errors or overtraced qualities to simulate human error if they aim to mimmick human handwriting.