HFS+ has been patched with duct tape and pieces of cardboard for 20 years; receiving journaling, support for Unix attributes, extended attributes, 64 bits sizing, multi-processing, multi-users, hard links, etc. over the years. Really it's a sort of monument to kludge. It should have been ditched like 10 years ago.
HFS+ is basically the Apple equivalent of an alternate universe where Microsoft just keeps gluing new features on to FAT forever and never creates NTFS.
I'm not sure that's terribly different from ext4's lineage, which is generally accepted (AFAIK) as a pretty good file system, even if not cutting-edge.
You might've missed Linus' second comment on the page, wherein he talks about case-insensitivity and NFD normalization.