So you're going to let a coach approach the stand and ask you about a back row attack AFTER you signaled legal? Not me. That's judgement.

It might (would) depend on why you said it was legal. "The ball was below the height of the net" -- sure, don't let the coach come over.

"It wasn't a third hit and the player didn't mean to hit it over so it can't be an attack" -- sure, the coach gets to come over.

And, yes, it's a little convoluted given the specific example given. But, the point is accurate.

But intent of the back row player doesn't matter. Only ball position relative to the height of the net and player position relative to the attack line matter. If a back row player didn't mean to attack but she attacked according to the rules then it is still an attack.

I know the rule. You know the rule. Felix knows the rule.

The hypothetical referee or coach in this thread might NOT know the rule. One or the other might make that statement.

If it's the referee, the coach has the right to protest to get the rule right. If it's the coach, s/he's still protesting about a rule--and will lose the protest and lose the TO (and if s/he has already used the two TOs will get a delay sanction).

No, I meant as in saying that something that is illegal to do was legal to do, when it is not.

If a coach wanted to protest that intent mattered, that would be a valid protest.

They'd lose, but since it's a question of correct/incorrect interpretation of the rule (and not judgement), it would be an allowable protest.

Judging ball height would absolutely not be grounds for a protest.