I once had an issue where GTK-2 couldn't display any characters that were in ASCII/latin basic. It was down to Pango dropping support for the monospace font I u

I once had an issue where GTK-2 couldn't display any characters that were in ASCII/latin basic. It was down to Pango dropping support for the monospace font I used for that range of characters. In my opinion the most reliable part of your system is the part you put the most attention on. ASCII is only the most reliable if you choose to use it as the basis for your system and then ignore support for everything else. Although I do agree the one character to one codepoint mapping of ASCII is useful, things like terminal escape codes already add a layer of complexity that makes it hard for me to imagine a scenario where you can't render U+1F4A9 but can still render things like ^[[31m found in almost every cli tool.