zanzibar: This is the nut of Harding's comment.
<Until Hübner (or the manuscript's owner) makes the source available for verification by third persons we are somewhat sceptical about admitting it to the Blackburne canon.>
Now, I like Harding's work, and his presentation (he generally puts useful lead-in info before extensive quotes, etc.).
This is an important point, and one I share with. <Missy> often nicks me for being cheap, but I do like utilizing open-sourced documents for my research. Not only as it does fit within the restrictions of my expense account, but also because it allows others to freely utilize primary documents, for their own purposes, as well as to check my own work.
Two other problematic works have entered the canon - but their lack of availably give me pause.
One is Gaige's 1994 (privately published) revised edition.
http://www.chesshistory.com/winter/...
The other is Townsend's 2011 <Notes on the Life of Howard Staunton>, which Harding has no problems citing:
https://books.google.com/books?id=4...
Of course, unlike Hubner, we know the actual source. But, Townsend's work was a pressing of only 100 copies:
https://www.abebooks.com/first-edit...
http://www.johntownsend.demon.co.uk... (not listed)
http://www.johntownsend.demon.co.uk... (it once was though)
https://www.kwabc.org/en/historical...
And if a source is no longer available, then even having the citation isn't so useful as it should be.