This may not seem like a big deal, but consider the effect that such an influential source of “correctness” can have on the general sense of what is correct. Spell checkers like Word’s are responsible for the “z” in British English being demonised. Once upon a time, according to linguist Gretchen McCullen, it was common in British English to use both z and s. But somewhere along the line, automated spell checkers cat…
I grew up in New Zealand and my mother was very insistent that I spelled and spoke "Proper English", rather than American English. This was before Microsoft Word was popular and the source of truth for the English language, especially for my tech-illiterate mother. She also didn't like me using slang, especially the Kiwi tendency to say "sweet as" and put "aye" on the end of sentences.
Maybe it's a colonial hangover, trying to hold on to the British identity, or maybe it's because she had a less privileged upbringing and saw "Proper English" as a sign of higher status.