My comments:

1. For labelDepth a bit more detailed description would be nice.
2. For me, the 'Chronological Order' at runWriterMonoid means just the opposite of the expected one, especially for lists.
3. Between runWriterMonoid and runWriterList it would be good to add that
   Free (Writer w) a is also a functor in w.

added test cases

Very nice kata, I feel I learned a lot!

A good kata! But tests should be improved:

• No random tests for local, labelDepth.

• modify is not tested.

Challenging but also interesting and satisfying! Would love to see more payoff at the end, e.g. using the monad instances in example computations.