Well, the “it” in my sentence referred to URIs.escapeuri — URIs.jl currently doesn’t have any functions for handling file paths, only URI paths, so this particular issue had nothing to do with Base.
Regarding your point, though, that splitpath and joinpath are currently only for the system you are running on, I agree that in principle it would be nice to be able to handle “foreign” file paths too. Though this doesn’t seem to come up in practice very often?
(However, it shouldn’t be an issue for @thestoicone in this thread the original thread, because they are using walkdir to generate file paths, and hence their paths will always be for the native OS.)