I've just read this question: What does size of a directory mean in output of 'ls -l' command?
...which doesn't quite answer my question. Basically, I'm moving files onto a NAS. The folders I've already moved are completely empty, with no hidden files or anything, and yet
du still reports their size at 3.5MB. Admittedly, they previously contained a large number of files, with long filenames.
Is this size simply because of the quantity and name-length of files that were in that directory? Why hasn't the size decreased now that the folders are empty (ext4 filesystem)?