The feature is not meant to encourage developers to use "my_cat" and "myCat" randomly within the same file.
Treating them as the same creates more danger -- the danger that the programmer intended them to be different, but the language treated them the same -- rather than mitigating danger.
I'm sure it's not, but it isn't doing a thing to discourage that. We stopped using case insensitive file systems a long time ago, didn't we?
Windows didn't.
But even Windows doesn't use an underscore-insensitive file system.
And its worse, especially when the variables aren't "foo_bar" and "foo_Bar", but, say, "cycle_often" and "cycle_of_ten".
Such an error is caught by the compiler.
const cycle_often = 10
var cycle_of_ten : float
ambig.nim:2:5: Error: redefinition of 'cycle_of_ten'