
Typically speaking I don't ever correct peoples grammar, because you never know how they will take it or even if they can help it - Maybe they have some variety of dyslexia or other difficulties. Despite being fluent in English, it isn't my native tongue and I still make mistakes - and the mistakes that I make are usually a habit (I often misspell the same words because the misspelling looks "right" to me) so even if I was corrected it wouldn't really do much. I reckon at the end of the day I would get annoyed if I was corrected a lot, even if it was polite and well meaning.