This may be an OS-specific problem. I am on Mac OS Ventura, Vim 9, and this seems to work perfectly.

TEST.txt and Test.txt are considered the same file.

This may be an OS-specific problem. I am on Mac OS Ventura, Vim 9, and this seems to work perfectly.

TEST.txt and Test.txt are considered the same file.
Screen.Recording.2022-11-13.at.18.56.39.mov

NERDTree seems to be unable to recognize filename case, which is a different problem. Please try renaming the file outside of vim. I am updating the issue to reflect this point. Thank you.

I still think this problem may be outside NERDTree; if at all.

I still think this problem may be outside NERDTree; if at all.

What you have done in this reply is try to match against the git filename matcher. Git is designed to be portable, such that the git filename matcher will preserve case but match filenames whose only difference is case. Therefore, git will show test.txt and TEST.txt as the same file. Because of limitation in Microsoft filesystems.
However the issue I opened has nothing to do with git.

It has nothing to do with Git 🙂

Now we know it's a filesystem issue. Maybe NERDTree could look into handling Microsoft filesystems better? I don't know a good solution to this. But generally files should be unique on their non-case-sensitive names. Hopefully someone with a Windows machine can look into this. I may not be of much help since I don't have the right environment to reproduce this.

Check that 'mv' is not an alias of 'git mv' in your shell. Unix systems(OSX, Linux, BSD, etc but not Windows) have case sensitive filenames.

Also, I see your machine is an Apple. I understand that some filesystems that OSX uses are not case-sensitive. So try to reproduce the problem in a Linux machine, which follows closer the POSIX standard in this regard.