If the selection begins with a :first-letter styled element the styled letter is not highlighted as selected (but is copied to the clipboard, more below).
However any following :first-letter styled elements are highlighted as selected.
If the selection does not begin with a :first-letter styled element all selected contents are highlighted.
The clipboard, once the selection is copied, includes the entire selection (rather than simply what is highlighted).
But the length of the selection, when testing the extentOffset property of the selection object, does not match what I'd expect. This sentence has 162 characters.