A Serbian woman on Quora told me uneducated native speakers of Serbian fail to use cases correctly, making errors like those who learned it as a second language, to the point on incomprehensibility? Is that really true? I asked her if she comes from southern Serbia (where this could be explained by the presence of native Torlakian speakers [which is part of the Balkan Sprachund and has grammar in-between Serbian and Bulgarian, with 0-3 cases) trying to speak standard Serbian), but no, she is not from southern Serbia. How could this be the case? I mean, children here in Slovakia know how to use cases as toddlers, from the time they start to speak in full sentences, long before they know what a "case" is, before they learn to pronounce r and l properly, and certainly before any "education", and most people who ever spoke a highly inflected language in history were completely uneducated and illiterate. So what is going on? Or is the woman wrong and what she describes is just some sort of severe diglossia present in some Serbian region?