https://gitlab.synchro.net/main/sbbs/-/merge_requests/415#note_4961

Because it's allowed in library and/or directory names, but SFTP reserves that character as a path separator.  Since lib/dir names can't have a division slash, it's a lossless, reversible translation that looks very close or identical to what the Sysop intended by putting a slash in the name.
--- SBBSecho 3.20-Linux