My kudos for the post!
A common problem appears when nobody fully understand the whole project, maybe because the project has become too big or because core hackers have left the project or because different expert groups have problems to synchronize their knowledge. A solution I have found to fight this scenario is to create a knowledge matrix, sort of a mega-index/summary trying to keep related information "close" and making it easy to search for topics so that developers can not just easely find docs they are aware of, but must importantly related topics they can not be yet aware. I use plain html and css. The result for a real project I'm involved at this moment looks like this: