Comments and strings, yes. And even though, non-english comments is considered bad practice at the non-english-but-international company I currently work for.

Comments and strings, yes. And even though, non-english comments is considered bad practice at the non-english-but-international company I currently work for. In identifiers? No way in hell. ASCII is small and well known and yet has its share of subtleties between \r \n \t and whitespaces and case-sensitiveness. The main point of ASCII is that it is really, totally, viewable without any surprise. Most programming fonts will be unambiguous, and won't make one letter appear like another: oO0, iIlL|1 Also, you can make monospace fonts for ASCII. One character can occupy a predictable space on screen. Unicode is another level totally. Not only do tons of glyphs look similar but also some of them are hidden, some of them reverse the order of the flow (LTR) some modify others, some (like emojis) are supposed to not be easily colorable. And of course, d̕ia̻̟̮c̨̤͚ri͍͕̪t̘̫̺͎̰̘i̯̫̱̻c̵͔̙̮̻̫͕̝s͉̹ make character expand up and down (I only went smoothly on this one, use http://www.marlborotech.com/Zalgo.html http://www.marlborotech.com/Zalgo.html to realize the magnitude of this mess) I once had to deal with a program written in Japanese, luckily in UTF-8. I was very tempted to propose patches using accentuated French and emojis. I'll be a proud defender of my beautiful French language any day, but as a programmer, we have the incredible luck of having more or less standardized on a language and a simple encoding. We should see that as an asset, not as a limitation. Imagine if Linus commented his code in Finnish. We can't have that.