Could you please split this issue into two parts, file names for open/create, and internal storage of file names; and give some priority to open/create? It seems that this part should be easy, and will alleviate the bulk of this problem for international Windows users.
There have been several patch contributions over the years, most recently this one from Christian Seiler which is well considered. Can something like this be included in the next release?
UTF-8 file name compatibility for HDF5 is impacting other communities, such as test failures when building netCDF inside a user account named with non-English characters.
Thanks for your consideration.