Mixx has suggested in
this post that calibre should sort accented characters as equivalent to their non-accented ASCII version.
What the suggestion means is that e, è, and é would be sorted as if they are exactly the same letter. There is no guarantee that one would come in front of the other. The same is true for c and ç, s and ß, A and Å, etc.
I have no idea what it means for non-latin characters such as Greek, Cyrillic or Chinese, but my guess is that they would sort using the letters that are used when creating file system names. It should (at least) be consistent.
Do you, the calibre users, want this?