Background... we have a lot of students with one name (not a first name and last name) and the institution has got around this by using '*' as the first name.
This requires the Windows operating system. I tested on Windows 10
- Create a new user. Make the first name just '*' and the last name anything you like.
- Create another user with a firstname and lastname just for comparison
- Create a course and create an Assignment within that course. Allow file uploads
- Enrol both students
- Edit both users submissions and add a test file
- Click 'Download all submissions' next to 'Grading actions'
- Open the resulting zip file in the standard Windows Zip program
The folder for the '*' user is not there as it would not be a valid Windows pathname (see https://docs.microsoft.com/en-gb/windows/win32/fileio/naming-a-file)
By comparison, it works fine in MacOS and Linux.
Before somebody says "don't use * as a first name", my point is that it is possible to create a valid user account with default settings that results in an invalid zip file in Assignment.