Whenever I get a typo from a friend, I ask them if they meant that word or the one they meant to spell. They usually snap at me and sat I'm trying to be smart with them
I find that people who tend to focus on another individual's spelling or grammar in a message medium are trying to feel better about themselves by making someone else feel "lower" than them. It creates the perception that they don't have enough achievements in their life to be proud of so they attempt to make themselves feel better by making someone else look bad.
Also quite popular among the moderation circle.