[lifthrasiir]

That's orthogonal to the module system. OCaml for example has `.ml` and `.mli` files for the same purpose, but `.mli` can be automatically generated from `.ml` if you want. And that's absolutely nothing to do with OCaml's great module system.

[flohofwoe]

Does the .mli file preserve documentation comments? IMHO the header file should be written for human consumption first. Documenting the implementation isn't by far as important.

[lifthrasiir]

The main OCaml implementation doesn't, but I believe there are several third-party tools that automate this. And as you've mentioned, comments in `.ml` and `.mli` do tend to differ, so even the default auto-generation may be useful because it will do as many jobs as possible without a human intervention.