I know I've brought it up before, but this is reminding me of the encounter with the Gith if Lae'zel is in your party. I think she should be the one Kithrak Voss addresses, and I don't think someone should be able to sub in for her possible deception check.
But there are certain other checks have clear justifications for other characters to pop in and comment, Shadowheart and Gale in the catacombs for instance. In fact having characters interrupt your characters musings to comment on something is an underutilized way of giving our companions so more opportunities to be fleshed out.
