I've realised that the expression problem applies to docs just as much as code.
E.g. for a PL, do you organise syntax highlighting docs with all editors together, or do you have a separate page for all relevant plugins of a single editor?
I really like the one-module-per-file model of JavaScript or Python.
If you're storing code in files, you might as well leverage file boundaries. If modules are a separate abstraction (e.g Rust, OCaml), it's harder to learn and choose how to organise code.