I agree, but the problem is that you don't ever want to do this whether those are three different variables (or is that two?) or whether all are alternative forms of the same case/underscore insensitive name. Nim is going out it's way to make the syntax you have about legal (will all of these equivalent), which strikes me as a bad move.

The best case for usability is that this "feature" never used, which makes it an odd design choice. The worst case is that the feature is used frequently, there is no clear language norm, visually scanning for variables is harder, search and replace requires dedicated tools, and subtle bugs abound. Far better (in my personal opinion) to make identifiers case sensitive and enforce consistency with style guidelines and code "prettifiers".

The current Nim approach is being called cs:partial (case sensitive partial) and makes the first letter case sensitive but all others insensitive. This like an awkward compromise, and needlessly complicated. The best proposal I've seen suggests making "_x" equivalant to "X" (underscore is an alias for "next letter is capital"). But I don't see it as better than case insensitive plus strong code conventions.