From reading the messages in this forum, this looks like an interesting article. Unfortunately I can not find it on the site. I find myself wondering about the basic cause of the library's constraints on access to the text. The instances I know of nowadays involve families having donated material to the library with privacy conditions. I think there are rather analogous cases of a university being chary with documents from its own history.
Older instances involve censorship of text deemed sexual.
When you get right down to it, I don't approve of donations made under such conditions. I am an historian, and it is my business to speak ill of the dead. They are perfectly legal under current property rights laws in at least most of the western world, however. I don't know. That might well deter donations to libraries, and I suspect offhand that documents donated to libraries get more use than documents kept by the family.