First and foremost, in my opinion, that a folder label is not a path. I might for example create a Syncthing folder on my Windows computer, label it
Fall/Winter 2019 because I deal with fashion, and share it to my Mac. The slash does not denote any form of hierarchy and the slash is not the usual path separator on Windows either. Creating directories called just
Winter 2019 based on this would be unexpected.
We must then also have logic to prevent escapes (
../secrets) and unexpected nesting of one folder inside another (
foo/bar/baz as two different folders). The latter would allow injecting data in another folder you don’t share or escaping (by pointing at a symlink in another folder).
It’s also a complication from the more general rule “odd characters are filtered when constructing the directory name”. We do want to continue filtering other specials like dollar signs and characters not possible in Windows file names.
All in all I’m very disinclined.