An example that strikes me is from english forums where many of the users don't have english as their first language. Maybe not at all. And yes there are large parts of the world where english is not a regular subject in school. A few example are Northern Africa (French and Arabic) and large parts of Eastern Europe (local language and Russian). So, we should try and take a breather before calling out the spelling of others. They might not have learned the language properly, just started learning it or maybe even trying to learn it on their own.