Word kerns nothing unless w:kern names a size to start at, and the Office
theme declares it on Title alone — but TextProps.kerning stored only the
off state, and a style inherits its parent's, so a title under a document
that kerns nothing could never turn it back on. Its 26pt line then ran
0.36mm over the text width and wrapped a word onto a second line where
LibreOffice sets it in one (measured 151.64mm kerned against 151.98).
Both states are stored now, and both formats read and write them.
A browser always kerns; ODF kerns unless told not to and Word kerns only
above the size w:kern names — nothing, in most files. Measured 5% on a
kerning-heavy string, enough to break a line a word early throughout every
Word document in the corpus. Carried on the style, since that is where
w:docDefaults and the default paragraph style put it.
Steffen Becker