Note by @cookingsteak

To make things simple, this world will have just one language in use during the current time period, with variable literacy/speech capability. Some people view it as important to be articulated, some don't. There are those who are interested enough in the world's past to learn to read other languages, but it doesn't have much utility otherwise.

Amphon can speak well enough, though he struggles with bigger words and certain sounds like X or rolling R. His reading ability is about the same. Wattana mainly uses very basic phrases (and has a raspy, worn voice from growling) and can't read words. Ae relies on the size of the letters to tell how important something is.