You mean like everyone running Windows, as well as anything using an ext filesystem?
-D Optimize directories in filesystem. This option causes e2fsck
to try to optimize all directories, either by reindexing them if
the filesystem supports directory indexing, or by sorting and
compressing directories for smaller directories, or for filesys-
tems using traditional linear directories.
Even without the -D option, e2fsck may sometimes optimize a few
directories --- for example, if directory indexing is enabled
and a directory is not indexed and would benefit from being
indexed, or if the index structures are corrupted and need to be
rebuilt. The -D option forces all directories in the filesystem
to be optimized. This can sometimes make them a little smaller
and slightly faster to search, but in practice, you should
rarely need to use this option.
The -D option will detect directory entries with duplicate names
in a single directory, which e2fsck normally does not enforce
for performance reasons.