Nim has a good reason to do it: library interop. You can use a third party library that for some reason uses snake case, but you want to follow the camel case that NEP recomends. You just do it, and your codebase is all in the same style. In fact, it the third party library updates their case, it doesn't break Nim code that depends on it (that happened for example to Python Selenium, when they went from camelCase inherited from Java to snake_case recomended in PEP8, forcing all dependent code to update).
I personally don't like that you can have "is_OK" and "isok" and "is_ok" in the same code as three valid different things. Or having "GL_FLOAT" and "GLFloat".
Both options come with tradeoffs. Don't jump so quickly into "that is a mistake" and allow the devs the benefit of the doubt. There is only one rule you need to remember in Nim: only the first character case matters.
That's not a good reason. Why not just standardise the entire ecosystem on the same style? If you think that sounds infeasible, consider that Rust, Go and even Python have done this with no problem.
That sound very close to "Rust is useless: why not just code in C without memory bugs?"
As menctioned, a few years ago Selenium had its methods in camelCase. If your code used Selenium, it had to be camelCase and snake_case mixed. When Selenium standarized, it forced everyone to switch to snake_case.
Nim puts great effort in FFI. It means you can easily use C libraries, using their names, even if the case doesn't match, and your code is still coherent. Look at the sample code in https://www.py4j.org/index.html : why do they end with "random.nextInt(10)" in their Python code? Didn't Python had this solved? Not saying that this is the end of the world, but the Nim way is not a mistake either.
Because an important feature and focus is that nim compiles to c and makes it easy to just import and use c libraries. So many of the 3rd party libs mentioned are NOT technically part of its ecosystem. There is at least one thread on the nim forum that extensively explains the reasoning behind the decision in much better detail and pretty thoroughly debunks this “problem”
I personally don't like that you can have "is_OK" and "isok" and "is_ok" in the same code as three valid different things. Or having "GL_FLOAT" and "GLFloat".
Both options come with tradeoffs. Don't jump so quickly into "that is a mistake" and allow the devs the benefit of the doubt. There is only one rule you need to remember in Nim: only the first character case matters.