Ideally, they would be respectful and mature enough that such measures would not be needed. Preferably, there would be precedent for polite, constructive argument exclusively on your turn to be the norm, and a certain amount of shame would be placed upon people who break that precedent. It is debatable whether such precedent exists, and given how the senate and the house of representatives operate, I'm inclined to believe it doesn't. However, in this debate, the precedent, whether it is for this style of debate or something more like I described, does not matter.
I don't think it is too political to either side to point out that the incumbent's main selling point is that he has very little shame, if any. Whether such a precedent exists is therefore irrelevant, since it works best to his strengths to ignore it regardless. He garners the most favor when he does exactly as he did here, militant interruption, making sure he is the last word, and saying whatever he has to to make the conversation steer towards where he wants it, even if it doesn't make that much sense in hindsight. The power in this strategy is that it completely shuts down every other strategy, since if no one else uses it or something similar then their speeches and posturing never reach the audience, as they keep getting stepped on, metaphorically.
A judge or regulating body given the right to silence all but one speaker is another way to make such debates more fair, mostly regardless of the respectfulness and maturity. The assumption would be that that judge was given that power by the candidates, and they are giving the judge the right to silence them, since that is what is most fair, and barring that, it is what is expected of them. You will note that this is the method implemented here, and in all presidential debates I can remember, but Chris Wallace's power in this debate is simply not respected, because the incumbent's strategy does NOT benefit from doing so. Therefore, the other candidate is under pressure to also not respect his authority, though you may note he tried to do so for a while.