I don't think it should be allowed at all, tbh. It's not allowed in tennis.
If the players can't win on their own, they shouldn't be playing - coaching is, IMO, what you do to prepare for a match.
I'm not sure if this is trolling or being serious.
I'm fine with people being against that, I don't know if I'm for or against it, but please choose a different reasons. Coaching is part of a competition to help athletes adjust and pay at their best. And... how do you want to control that anyway?
A "Good!" after a rally is coaching, even nodding, a smile, or a thumbs up is.... That's just natural to come out. If you allow any of that, where do you draw the line?
Not allowing coaches near the court?
They could sit/stand elsewhere.
Ban them from the location and limit their access to the training location?
That means no coaching even between games. I'm certain it would lead to worse games, much more one sided, because it's much harder to adjust without input from the outside. Athletes should focus on the game they play and having somebody suggesting/dictating the rest from the outside - while providing a ton of mental support - helps them do it.
I'm not a fan of coaching between points, but it just doesn't work to allow coaches to be able to have coaching at certain times and expect them to not do anything between rallies - or even penalize the player for that.
It needs to be controlled, certainly. I sometimes feel like it's a bit too much, too, but overall, I think it's not too bad.
Reducing coaching to the preparation before the game is just... I cannot think of a nice way to finish this sentence.