Oh, this is such a fun rabbit hole.

There are plenty of programmers who can write a commit message in almost perfect English, yet don't know the difference between lettuce and radish, and can't tell what a little sheep is called.

My favorite area to catch people on is religion. Many C1 English speakers who grew up religious, some of whom are still devout and go to Church every Sunday, would be unable to hold even a basic conversation about their religion in English.

The unfortunate side of this is how non-native speakers of English swear much more often. I got better at it, but I suspect I'd still struggle in American corporate culture.