[mort96]

I don't understand your LFN example. Which FAT file structure can be represented with LFN disabled that's no longer possible to represent if you add support for LFN?

If BigFAT was actually backwards compatible, it would've been a no-brainer to add support for in filesystem drivers. But since it changes the interpretation of some legitimate structures, adding support for BigFAT is a breaking change. I don't know whether operating systems will want to make breaking changes to their FAT32 filesystems, but it certainly seems like a bigger ask.

[DannyBee]

Err, a directory with all possible six character prefixes, differentiated at the seventh character, is representable without LFN but not with it. Wikipedia actually has links/info on it if you want more.

[lproven]

My favourite sobriquet for MS has long been the DOS view of an Office 97 installation in the filesystem:

MICROS~1

(Long name, Microsoft Office.)

So if you create files called MICROS~2 - MICROS~0 in theory you can create enough abbreviated names that there are not available short names for long filenames you wish to create. Every LFN must have a "real" 8.3 counterpart.