For the first 2 minutes, candidates ought not interrupt each other - and the microphones of the NON responding candidates ought to be cut off for that time.
Maybe leave both mics on during the open discussion part.
Chris Wallace clearly favored Biden - but then, he always was a bit of a lefty. I remember when he was interviewing Pat Buchanan during his presidential run he asked "Would there be any place in a Buchanan administration for David Duke?" Pat instantly gave a one word answer - NO - and shut up. Wallace wasn't very happy.
Back to the debate - Trump scored a hit when he said he was debating Wallace as well as Biden, but I thought he interrupted too much; I think he could have scored more solid "hits" on Joe if he'd waited his turn to talk. Biden spewed nonsense and was never called on it by Wallace, but since he didn't soil himself or wander aimlessly off stage, most media ABCNBCCBSMSNBCCNNNYT pundits will claim he won the debate.
Me, I would have debated Biden a bit differently than Trump did, but hey, I'm not a billionaire living in the White House, so what do I know?