should the fact that `this` is bound to module.exports be documented?

```
% node -p 'require("./f.js")'
{ fu: 'hi' }
% cat f.js
this.fu = 'hi'
```

This is not documented, should it be?

cf. https://github.com/nodejs/node/pull/9622#issuecomment-260727547 and earlier comments