It's good to be polite. Can't argue with that. It wouldn't be polite.
But there are times when it interferes with recording. And we can't have that.
When I interrupt someone, I feel terrible about it, because I hate being interrupted before I can finish a thought. So I'll be deferential, raise my hand to my mouth, and say "no, you go." Then they'll say the magic, destructive words that restart their thought...
"I was just gonna say."
Listen for it. You'll notice how much it happens. And if you've ever had to edit a podcast, it will drive you mad.
We record all of our shows over Skype. This introduces lag and delay, yes, but it also removes the visual element of conversation. You can't read people's motions while they're talking to see how close they are to a pause, and they can't see you taking a breath to start your point. Without that visual element, train wrecks are bound to happen.
There are two main ways to get around this when you're podcasting remotely:
Get more gun-shy about cutting in with your points. Things just don't move fast enough for you to fire off your point right when it occurs to you. Focus on listening to another speaker while you formulate your thought, so it's ready to go.
Podcast with the same people for a really, really long time, so you can learn their rhythms.
Even still, train wrecks are bound to happen. But that's okay. You can edit it out.
Unless you begin your thought with "I was just gonna say..."
My tip for anyone going into conversational broadcast is to nix this from your vocabulary, because even if the producer can edit out the interruption, they can't edit out the traces of the interruption if you start your thought with this infernal apology. Nobody naturally begins a thought with "I was just gonna say." "I was just gonna say, pizza is cool" isn't a real sentence. But that's what will come out of your mouth in the final edit.
If a trainwreck happens, pause, recognize it, and pause again. Then decide who will continue speaking... Then pick up with your thoughts as if nothing at all happened. If the podcast you're on is one where they edit with markers, the producer will have already made a note of it, and it will edit out smooth.
So, the moral is, you weren't "just gonna say." You just say.