It was on Wikisocion, before the big crash. I did find the original Russian article, which you can translate using whatever machine translator you prefer: Ãóëåíêî Â.Â., Ìåãåäü Â.Â. "Ñîâìåñòèìîñòü è äóàëüíîñòü"

In order from most compatible to least compatible:

D+N, C+H = "subtype duality"
D+D, N+N, C+C, H+H = "subtype identity"
D>C>N>H>D = "subtype supervision"

In other words, the Irrational subtypes get along best with other Irrational subtypes, and the Rational subtypes get along best with other Rational subtypes.

Of course, that's assuming all other factors are equal, which they usually aren't. Base type compatibility is still the main determiner of deep, inner compatibility. Subtype compatibility is more about surface-level, daily-life compatibility.