I had a scene with Shadow Heart (In camp) where Gal added something. Same with Wyll and Karlach. And Astrion....
I've had those same conversations, but they were all for very specific plot points in the companions story line. Astarion for 'coming out' if you will. Wyll and Karlach for obvious reasons. And those were all mostly 1 - 2 line reaction comments on what a specific companion just revealed to the party. Other than that though, none of it (that i've seen at least) feels organic. idk, maybe I'm just not getting the same conversations as other people.