Mergesort Conclusion
Embracing low-level asymmetry and addressing high-level bi-symmetry elegantly improves the trade-offs of the decade-old Mergesort-trilemma. The symmetric definition of sorting guides the development of stable algorithms, and exploiting buffer-asymmetry in symmetric-merging (and stable symmetric partitioning) allows to reduce the amount of buffer required, in some cases even using less energy and sorting faster (Frogsort2).