Comment 14 for bug 49217

I don't doubt that you can use a bad character in a Linux
implementation. Also, the vfat module and dosfsck are not the same piece
of software and both read from the drive in completely different ways.

My point is that dosfsck is checking a FAT file system. The problem is
not that these characters are allowed in some cases, but as I understand
it, not in all cases - that is, under some code-pages those characters
are not allowed.

Trying to determine the correct code-page for the appropriate
file-system is the real issue. Once that has been achieved, then
determining which characters are "bad" for that code-page becomes rather
more simple.

Just arbitrarily allowing any old bad character defeats the process of
actually checking the file system.