I'm not too familiar with the specifics of Nim, but how are case-insensitive variable names a bad idea, except that notion is so unfamiliar to programmers?

Flipped around, if a language were to be designed today in a vacuum, what is the argument in favor of case-sensitivity in variable names?

My feeling is that we take case-sensitivity for granted because the vast majority of languages inherited that behavior from history's lineage of great programming languages. But re-evaluated without that history, case-sensitivity seems only to create potential confusion at best and opportunities for trolling and obfuscation at worst. Today's use case to indicate scope, mutability, or permissions is an artifact of this history. As programmers, we know how to read something like this in Java, but if we were able to completely erase our historical knowledge and consider language design without that baggage, this seems like bad language design:

    // Local variable square is instantiated equal to 
    // SQUARE constant in class Square.
    Square square = Square.SQUARE;

Admittedly, a statically analyzed language will have most case typographical mistakes found and corrected at compile time, so they are a lesser annoyance than case-sensitivity in other contexts (such as filenames or column names in database tables). Generally speaking, I would be in favor of a hard break to drop case-sensitivity across the board, but I'll put that on the same list as adopting the metric system in the US (titled: "LOL, good luck.").