My response to : Should Coaching Be Banned in the FGC?
Be it during a match or in between sets, coaching *is* cheating because a 2df game in its essence is a *mind game*, and will never be a physical challenge.
You definitely have things like execution and muscle memory as physical obstacles to overcome, but that's for novice players only. You should already be past those issues to even consider yourself a mediocre/casual player. So What's left is purely a technical, psychological battle in which *mind games* decide the outcome.
Patience, guessing, reading, conditioning, baiting, concealing, holding on your ace, adapting, memory, reflexes, taking risks, awareness, resources monitoring, stress management, framedata/hitboxes/bugs knowledge, knowing your character, knowing your opponent's character, playing ignorance, playing the victim, playing low, keeping background tabs on your opponents, studying tapes of yourself, approaching with the right mindset, maintaining that mindset, getting over bad habits, thick skin, luck, modesty, grace, faith...etc, none of that stuff is physical now is it?
I see that it's clear as day that two people combining their minds' power against one person is unfair in many levels. That same person is now feeling an additional pressure when they realize that they have to beat two and a half persons.
And then there is the question, who is coaching the coach?
 Of course unless you have an illness or a disability preventing you from playing normally.
 One could argue that this is physical and can be trained as, say, execution. But since it happens mostly in the mind and is extremely hard to obtain when your mind is weak, I'll keep it in the psychological list.
 Because the coach has far less strain on him that he can evaluate stuff better than an engaged person.