> A utf character from a language that has zero chance of being mapped to your programmer's keyboard in the middle of a code line, that would be obvious intentional tampering or at the very least raise some eyebrows.

I accidentally get Cyrillic "с" in my code few times a year. It's on the same key as Latin "c", so if I switch keyboard layout, I don't notice until the compiler warns me. Easy to do if I switch between chats and coding. Now my habit is to always type a few characters in addition to "c" to check what layout I'm _really_ using.

Granted, it's easier with a one-letter variable called "c", but with longer names I can easily see myself not typing "c" the first time (e.g. not pressing hard enough), starting build, chatting in some windows, getting back, facepalming, "fixing" the error by adding "c" or "с" depending on my keyboard layout.