Implemented, except not done using '_' because the new Sitemap has proper deep positions for help screens.

However, special hard-coded rules have been added to hide help pages specifically from Google. This is justified as Google results for site-specific help, which is available contextually within the site, are not appropriate.

advertise/donate pages may already be automatically removed via the Setup Wizard, and other default Comcode pages are in separate addons. If not removed, it is correct that they should be indexed.

Additional use of overlays is implemented in a couple of places.