My favorite namespacing syntax is ironically Clojures. module/func or fully.qualified.module/func or just func if you explicitly import the symbol. I vastly prefer shallow namespacing (module/func) most of the time.

I write Rust mostly for my day job (and it's also my preferred language on the side these days), so I usually end up explicitly importing all the symbols I actually use because module::func is just additional noise in an already pretty verbose language and is what's considered 'idiomatic'.

I don't really get the issue with :: being the separator used here. It's slightly ugly, but it's visually distinct from . for field access, which I do appreciate.