Currently quaternion negation takes the conjugate rather than scaling by -1, which was surprising to me and doesn't seem consistent with binary operator -, which indeed subtracts memberwise.

This seems to be a regression introduced many years ago at e7bf99e#diff-f11831298dd6e7900532989a327b8f1934d513eb3e33faa366c68c1a44227c5eR377

This applies to both vector_math and vector_math_64.