  We identify computability-theoretic properties enabling us to separate
various statements about partial orders in reverse mathematics. We obtain
simpler proofs of existing separations, and deduce new compound ones. This work
is part of a larger program of unification of the separation proofs of various
Ramsey-type theorems in reverse mathematics in order to obtain a better
understanding of the combinatorics of Ramsey's theorem and its consequences. We
also answer a question of Murakami, Yamazaki and Yokoyama about pseudo Ramsey's
theorem for pairs.
