MATLAB writes its .m files in ASCII encoding, meaning that any non-ASCII encoded characters are replaced with the character '?'. Though MATLAB can display characters in other encodings in the Editor or Command line, it will write them as ASCII if a user saves the m file using the MATLAB editor.
A workaround to this is for the user to write this to an MLX file instead. If you create a file with just the following:
Saving it to an M file and reopening will have the characters appear as a question marks. Saving this as an MLX will retain the characters upon reopening.