We all know that light speed delays become significant at interplanetary distances. I say something, then I have to wait for it to get to you, and wait for you to reply back.
And by the time anyone is flying interplanetary distances, I'm sure that we'll all be quite used to video chat, and that we'll finally have videophones.
But I think it should quite clear by now, nobody is going to just sit and wait for the delay.
Right? It's IM, not a phone call. As soon as the delay gets to be more than a few seconds, communication is asynchronous, and you start multitasking. So when the captain of the spaceship is having a tense exchange with some politician back on the ground, he's not going to say a single sentence, then sit there uncomfortably in front of the camera for six minutes while the radio waves trudge back and forth.
It'll be like this: he works on something else while waiting for the reply. His wall-spanning video screen goes "bing" and notifies him that he has a new message. He finishes his current task, then plays the video. He thinks about it, plays it again, and only then does he activate his camera and reply. And when he stumbles halfway through, he stops the recording and starts over. When he's all done, he hits "send" and then goes back to doing whatever he was doing. It's like how we manage email or discussions in, say, blog comments.
Heck, you could do it that way right now, right? It's not even in the future, it's right now! So, science fiction writers of the world, this is what I expect from now on! This story was published in 1996, so I guess it can be excused. Everyone else, you're on notice!