That's a circular argument. They are different only because the language says they are different, while the post you've responded to says (correctly) that that's bad language design.

The bit representation is different.

Which is irrelevant, since languages are a medium of human expression, not a way to store bits on the disk.

Irrelevant to what? The two words literally are represented with different bits (code).

Assuming you are not trolling: yes they are indeed represented with different bits, which doesn't matter since these bits are not the bits executed by the CPU in the end. The "words" and not the bits are interpreted or compiled into machine code. Which is where bits matter.

clearly case sensitivity is a decision by the language designers. Many languages are case-insensitive.

from https://en.wikipedia.org/wiki/Case_sensitivity

Some computer languages are case-sensitive for their identifiers (C, C++, Java, C#, Verilog, Ruby and XML). Others are case-insensitive (i.e., not case-sensitive), such as Ada, most BASICs (an exception being BBC BASIC), Fortran, SQL and Pascal.