As a frequent canoe race primary bow paddler, the worst thing to do is to overtalk the stern paddler and miss a "hut" call. I have to occasionally talk to relay conditions ahead, but will try to wait until just after a hut and get out all of what I need to say before the next hut. Usually, the timing of huts is regular and known by paddle stroke count, except when a turn or maneuver is upcoming. Being bow paddler in a 7-seat voyageur canoe, it can be difficult for the stern to hear what i have to say and vice-versa. I will continue paddling at team pace rate while turning my head to the side to speak loudly enough and to hear. My hearing is good, but sometimes paddler in seat #2 will have to relay to me what is being said from the stern area, especially when in strong wind or waves when I might not hear a hut call. During long boring segments of the Yukon River races, sometimes a conversation is struck to break the boredom. Done between hut timing. On the 1000-mile race, our canoe was unintentionally divided between 3 paddlers in the front, then a pile of gear separating the four in the rear. Each section tended to have our own social conversations.
When I am instructor for BSA guide trek leader training, we stress to students that conversation must be at a low level of conversational speech, which they should carry over to when they are later guiding scouts. If a canoe gets too far away to easily hear another without shouting, then it is simply too far away, which is against safety and LNT policy.