> This results in a truly hierarchical, filesystem-like data format. In fact, resources in an HDF5 file can be accessed using the POSIX-like syntax /path/to/resource.
That seems a whole higher level of complexity compared to CSV or the other options listed in TFA (perhaps comparable to Excel).
NetCDF4 (built on top of HDF5 largely through sub-setting) is considerably more powerful than excel/libreoffice. Its also easy to access through widely-available libraries. I frequently use the Python `netCDF4` (yes, it really is capitalized that way) library for exploratory work.
That seems a whole higher level of complexity compared to CSV or the other options listed in TFA (perhaps comparable to Excel).