This change fixes an issue where a file/directory is not created when its name contains trailing spaces or dots.

It would seem that trailing dots are created, but the dots generally aren't shown and the name counts as a duplicate to without trailing dots or a different number of trailing dots. That's not an objection to stripping them or anything, mind.

I see your point. Actually, the current implementation would also treat file? and file: as duplicates (since both of them will become file_), similarly for other pairs of illegal characters. I think that a complete resolution of this is impossible, since the user could theoretically name the file to any of our mitigation attempts :). But maybe it would help to replace the illegal characters with their encoding of some kind (URL-like, UTF8, maybe even ASCII)? It would make an accidental collision a bit less likely.

No, I don't consider that a concern. I was describing the behavior of the /mnt/onboard filesystem on Kobo for the sake of accuracy. Only trailing spaces are problematic, give or take the edge case of trailing spaces followed by trailing dots. Creating a folder with the name test. works with any number of . (as long as you stay under 255 characters total I assume). But test or test . will not.