I am a self-taught writer. I dropped out of middle school at a very early stage. I really just read enough books as a kid (hooray libraries) that I can stare at a sentence and get it mostly right. There are many times I do not get grammar right because I was raised by grammar wolves.

That’s to say: everyone comes from different backgrounds. The primary purpose of writing is to be understood. If the writer achieves understanding in their audience, they’ve gotten 90% there and you should be less of an asshole about it.