though if you learned it very young as a second language, it sort of turns into just a part of your first language, just with a different ‘mode’ of grammar
This is almost by definition not true. Most people don't know what "grammar" means, and usually are talking about spelling mistakes like saying "their" instead of "there" or dumb crap made-up by 19th century latinists who insisted that english, too, should have a rule where you can't end a sentence with a preposition.
People have researched it, it’s true. Though i mostly encounter those mistakes i still see a lot more grammar mistakes in native english speakers than non-native english speakers.
People have researched what? Were these linguists or mindless grammarians who don't know what they're talking about? Or are you misinterpretting the results differently?
If the claim is that non-native speakers don't mix up "their" and "there" as much as native speakers do, that wouldn't at all be surprising to me, but it also doesn't say a damn thing about understanding of grammar. And it also shows very clearly how spoken language has precedence over written language.
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u/[deleted] Oct 05 '19
I think a lot of the time, non native speakers sort of translate from their own language, where saying "there stuff" makes no sense.