[The deaf] can comfortably sign while watching someone else sign. In large groups it still makes sense to have one "speaker" at a time, because people cannot look in more than one direction at a time, but conversations between pairs [have more overlapping communication than spoken conversations, as if they talk and listen simultaneously.]
[Conversation is best as duet over duel: each positioning the other to say great things, playing for the game and assist rather than the score.]
[Debate features adversarial "zero-sum" conversation, where weakening their position is as good as strengthening yours, and largely militaristic metaphors of] defending a statement, attacking a position, falling back to a weaker version of a thesis, countering one accusation with another.
[An alternative to the debate game could be one where two sides are given seemingly incompatible objectives for an upcoming legislation and scored on how well they argue that it supports their side. The score of each side added up and given to both sides, so they rank higher by collaborating more.]