But why this unusual level of scrutiny? The book is published and endorsed by both Google and O'Reilly, two of the most respected brands in this domain. Why are they not a satisfactory "third or first-party confirmation of expertise" but random commenters on Hacker News would be?
Because I do not respect the brands or general reputation, so I would like to know if there is substance underlying the reputation. If the reputation is built on truth instead of marketing, I would hope that there are examples of substance where they achieve what their reputation says they can do. I believe this an appropriate general strategy if one does not believe in the reputation, so this is not really an unusual level of scrutiny, it is just that I do not believe in the brand where as you do (not that there is anything wrong with that).
As for random commenters, since I can not use the reputational apparatus for information, I would need to get direct information. There are likely people here who work with the stated individuals, so there is a non-zero chance I could get that information. Hopefully random commenters would not lie for no reason, but to deal with that I avoid incorporating information that can not be cross-referenced.
