The effect is somehow also visible in the shapes of the letters, with ‘B’, ‘O’ ‘U’ being rounded and soft. The letters ‘K’ and ‘I’ are made of sharper shapes featuring triangles and lines. I wonder if letter designs were influenced by the sounds made by objects.
I distinctly remember trying to "read" sentences as a small child by investigating the shape of the letters. For example, if a letter looked friendly, like like A or C, I assumed a nice message. If the letters looked serious or grave, like T, E, K or W, I assumed a bad message. If a letter looked soft like B or P or O, I assumed the sentence was about something soft, etc.
Particularly, the degree of sharpness or roundness of a particular letter may have changed a lot over time. I guess it's still possible that there's been some kind of psychological effect at certain times, but it doesn't look like it was a strong and consistent factor in the history of the alphabet.
That is because of the focus on writing itself. Its easier to make sharper letters on clay tablets, making such letters on palm leaves ( popularly used by some cultures for writing) would tear the leaf, so the writing became more rounded in these regions.
You might be interested in Ink and Switch's 'Inkbase' [1] concept. I'm not sure it's ready for Android tablets yet, but it seems to have a lot of potential for 'programmable' ink like you're describing.
