all the ways in which terminals' text rendering is bad
terminals really want text to be a 2d grid of characters which can be rendered by just mapping each character onto a box on the screen. now, if your language uses a latin script, this can probably be made to work good enough. unfortunately, it turns out that language is complex, orthography is complex, and if you try to generalize this approach to text rendering to handle unicode properly, you're gonna end up with Problems