"Embedding docstrings in with the source also imply that functions and macros should be documented as they are written"
Not at all! It's been a mind-blowing experience to me to see documentation pop up in all of the arc codebase just because we had a wikipedia-like workflow.
People often don't want to talk about what they're doing when they are doing it. It's just human nature. This suggests another great time to document code: not when you write it, but when you read it and figure out what it does. A wiki allows this.