Calibre may be at fault if it is unexpectedly changing the hyphenation behavior, which is then propagated by the Nook bug until reset. Earlier in the same thread mentioned in the original post,
Peter Sorotokin suggests:
Quote:
This property is better suited for hyphenation control:
Code:
adobe-hyphenate: none | explicit | auto
|
So, try adding (say)
Code:
body {
adobe-hyphenate: auto
}
to Calibre's extra CSS.