Thanks all for investigating and discussing this issue. I'm reviewing the PR, and I can't help but wonder, does this same issue exist when building with setuptools? Do you care about older Python versions? Would addressing these issues in setuptools address your needs?

Additionally, the main use-case you describe is someone wishes to create an sdist referencing invalid filenames. That seems like an undesirable case. Could such a project not instead generate these invalid filenames on demand rather than materializing them in a distribution package?

I'm also concerned that by altering `write_file`, we're applying a change for a specific use-case to a utility probably shared by several use-cases.

Overall, I'm leaning -1 on this right now. Can you convince me this change is the best thing for the system?