> it can be used to distinguish someone that learned English writing rules in a formal educational setting versus those that did not. Sure, this might be true,

> it can be used to distinguish someone that learned English writing rules in a formal educational setting versus those that did not. Sure, this might be true, and I'm aware that it's what you meant, but it's not the same as being a way to distinguish native from non-native speakers (or even writers). Many, many non-native speakers got to quite advanced levels of formal English writing via formal schooling, especially in places like Northern Europe. I suspect people like that are actually more likely to avoid ending sentences with propositions than native speakers are. I think what the person who started this sub-thread was referring to is stuff that really is intuitive for every cognitively normal native speaker, like the difference in meaning between "the dog bit the man" and "a dog bit the man". Practically every native speaker, including illiterates, would agree on whether "the", "a"/"an", or no article at all is correct in any given situation, whereas it's very difficult for many even highly educated non-native learners.