For a newcomer in Domino development, the documentation exposes all the "history" of Domino development.
Some of theses features are clearly no longer recommander to be used or can't be. For example NSFDB2. But when you read the documentation with the eye of a newbie, you can start digging in this interesting feature.
I would recommend tagging part of Documentation with a Deprecated flag, maybe with different level (must not / should not / may not)
I think it's also valid for Admin documentation