Pesky spellcheck!
It’s the little niggles that come to hurt most, like the spellchecker that doesn’t know whether we should use there, their or they’re, so often tries to miscorrect us. After days of that, I’d had enough and disabled checking completely. All my errors were then my own, which is comforting but not helpful.
Cupertinos, the term for these spellchecker miscorrections, goes back to the 1990s, when European translators found the unhyphenated word cooperation being changed to Cupertino.
When revisiting this, I found an option in the contextual menu which offered to learn my deviant usage. Oddly, learning better behaviour isn’t always a choice in the Spelling and Grammar panel, but once taught this and my other quirks of English usage, it’s surprising how much better these checks have become.