> "They were the ones who caught the mistakes that no spell chequer could."

I thought that maybe "spell chequer" was the valid British term, which would be interesting, so I searched but it isn't. It turns out that the joke here is that "chequer" is a valid British word, so a word-based spell checker won't flag "spell chequer", so it's self-referential. I see why people found his jokes actively confusing.