In that same post Lighter also cited:
1908   K. McGaffey Sorrows of Show Girl xiii. 157   He being a nervous party springs a blue note that got the musical director hysterical.

And in the post immediately before that Phil cited a 1915 newspaper article which quotes the pianist in a night club using the term "the blues" as a plural noun referring to blue notes:
"A blue note is a sour note," he explained. "It's a discord – a harmonic discord. The blues are never written into music, but are interpolated by the piano player or other players. They aren't new. They are just reborn into popularity. They started in the south half a century ago and are the interpolations of darkies originally. The trade name for them is "jazz."

Until those posts, the facts had showed that the term "blue note" wasn't used before 1913 and could not have been the source of the name of the musical genre that was called blues as early as 1910:
- People talked of "blue notes" in the 1910s in connection with what was already known as blues music.
- "So by 1908 the public... called it 'blues'..." I don't know of any evidence that anyone was thinking there was a type of music they called "blues" music before 1909. (What people called blues music, starting in about 1909, included songs that predated 1909.) Handy's 1926 book claims that the idea of blues music as a type of music was known in various states during the year 1910, but only arose shortly before 1910. The other evidence we have (Kid Love playing "Easton Blues" in Texas in 1910, for instance) supports that book's claim.
- What became known as "blue notes" in the 1910s, because writers were encountering and interested in blues music in particular...
- Page 2 of the 1913 edition of "The Memphis Blues" says "... Song Founded on W.C. Handy's World Wide 'Blue' Note Melody." That evidence of the use of the expression "blue note" is from several years after the earliest evidence of the idea of "blues" music, such as the 1910 article about Johnnie Woods.

As I said earlier in this thread, when something doesn't make sense it's a clue to me that I don't have all the facts.