Since I'm no aficionado of British royal jewels and only had a quick look at the Instagram account in question, would you mind giving a link to an example of what you so nobly described as information which will not be found in published books?

Pinterest and copyright is a particular pet issue of mine. There's a possibility to prevent saves to Pinterest by adding a short code snippet to the head section of a website and a way to turn off saving to Pinterest on a single image by adding a tag, but I don't see a possibility to apply either to a message board.

Prevent saves to Pinterest