Farmer Oak was humble (one characteristic) and at least a little honest (half a characteristic).
It says nothing about Bathsheba's humility or honesty; you have to infer she was neither of those, since she doesn't seem to like them in other people.
(I had to look up "moiety.")
And no, we don't usually talk about "half a characteristic. This was the author's playful choice.
Student or Learner