> It's easy for a non-native speaker to make a mistake in informal language after reading formal material like the aforementioned, and it might not be great to

> It's easy for a non-native speaker to make a mistake in informal language after reading formal material like the aforementioned, and it might not be great to call out minor breaches of etiquette in such a targeted and public way. It seemed to be addressed in a respectful and understanding manner, what's wrong with helping someone (and apparently a bunch of bystanders) learn from their mistake?