[schmonz]

Writing Ikiwiki plugins is often very easy, because triggers for most events you'd want to get involved in are available, and because much of Ikiwiki's own functionality is implemented as plugins. Reading and understanding internals, as you point out, can be challenging.

Tricky and/or important bits of functionality are often covered by automated tests (and I've test-driven new functionality in: http://www.schmonz.com/2013/08/22/tdd-by-example-an-ikiwiki-...). A sufficiently motivated person could incrementally test-protect more of the internals and refactor under test. I hope to have more time for this soon.