audacity supports installing local quick help and manual pages, but they aren't installed by default and there isn't a use flag to install them. Other packages have a "doc" use flag for this purpose. It would be even more helpful if all packages honored this as a global use flag to install documentation with every package when provided.
i can see the code fot this in the 2.4.2-r1 ebuild so closing this bug. if you meant something else then please let me know.