There is a reason old languages were many times case insensitive but not anymore.
Regardless, this does not preclude the use of Nim any more than a regulation saying "do not use preprocessor macros" preclude C because you might accidentally use #define. It just means you have to verify that you adhere to those regulations. Here's one tool[0] you can use to make sure your unconditional requirements are satisfied.
Nim would probably be precluded anyway based on age and popularity, and rightly so for tightly regulated industries -- but given some time, assuming it does grow in popularity, there is no inherent reason Nim would be precluded from any project that allows e.g. C++, Java, JavaScript or Go.
If this is the goal, there are many alternative ways to solve this problem, making the language case insensitive is a pretty big hammer.
Case insensitivity is a feature and it's meant to allow easy interfacing with C.
And it also encourages clean code.
With other languages you can have variables called "startdate", "start_date" and "startDate" in the same scope leading to bugs - especially when using completion in an editor - and poor readability.
In Nim the compiler tells you that you are redefining the same variable in 3 different places and you can go and give them more meaningful names.