Semantically, you're right, this is not strictly an error. A warning is more appropriate here. However, in `node`, `console.warn` and `console.error` both emit to `stderr`, so the difference is academic.

I tried to think of a different place to put the verbose and silent flags, but nothing makes as much sense as the env object (I get nervous about bloating it too much, but then realize it's just a lightweight object with a series of properties...). I like the approach of a utility logging function, similar to `less.writeError` in `lib/less/index.js`. It would allow a central point of config evaluation, formatting, etc. However, that pattern would involve a lot more monkeying around with scope and whatnot, since `functions.js` does not have access to the `less` object, nor is there currently a concept of "global" config flags (instead, they're copied and passed around).

For now, adding `verbose` and `silent` to the `env` flags will do. I'll patch it later today.