[QUOTE=theducks;4015877]Why are you using a folder-file system on a Kobo anyway? It uses a Library manager and AFAIK does not expose the FS to the devices user.
Or have you rooted your Kobo?
I don't think you can root a Kobo since that seems to be an Android concept. OTOH, the Linux system running on a Kobo is open which is what makes it so easy to patch. Kobo also allows user access to the database which makes a lot of operations (collections, series, subtitles, Ghod alone knows what else).
The file placement dates back to before I started using calibre since I prefer not placing all my books in the root directory. I simply carried over my directory structure when I started to use calibre since calibre by default would place all ebooks into the root directory. Given that virtually all my ebooks have long filenames, it is relatively easy to run into the limit on the number of directory entries in a FAT32 partition. The eLib/author-sort/ helps to turn that possibility into an improbability while trying to avoid running into the path length limit. A quick check on my Clara HD which was modified to have a 32GB uSD card shows that if I placed all my non-fanfic ebooks in the root directory, I would be using 57,437 directory entries out of a max of 65536. Adding in the fanfic ebooks would break the system whether I tried placing them in the root or in a single subdirectory.
The FAT32 partition is exposed when you connect via USB and with a bit of work, you can telnet to your Kobo and have fun with all the partitions.
For those who have not already been bored to tears, a LFN entry takes a minimum of two directory entries and a maximum length 255 character LFN would use 20 directory entries. So a FAT32 root directory can have at most 32,768 LFN files and with all names at the maximum length, you could only have 3,276 LFN files. Subdirectories start subtracting from the maximum LFN length due to path length limitations.