Serve
 

Team S is serving. As S1 tosses the ball in the air, ALL the members of Team R YELL "Jump". Or as S1 is about to contact the serve, ALL the members of Team R YELL "floater".
This occurs on every serve.
If you are R1, do you address this behavior? If so, then what do you do?

"It depends."

If it's for communicative purposes, even though they should be able to see what type of serve is coming, I've got nothing.

In the rare instance when you can be 100% certain it's merely to try to be unsporting, you can address. I believe NFHS specifically addresses attempts to disconcert the server, whereas in other rulesets, you could use the "no yelling at the opponent through the net" guidance.

But don't look too hard for trouble; otherwise, you'll find it.

This was a lower level High School game. I did inform the Coach and Captain that this behavior could warrant a Yellow Card. They DID NOT like my guidance but They ceased their YELLING.
Funny thing. After the game, 3 parents thanked me for curtailing the yelling during serve. Two of the parents were from the team committing this behavior.

I can say in Michigan I posed this question to the then head of the MHSAA for volleyball and her response was this was a cardable offense because it was done in an effort to distract the server not for communication purposes.

I thought then, and still think it is a slippery slope to call and to me would have to be obvious. Given that most teams have a team leader on the floor, it isn't shocking to have 1 person call something about the serve, but all 6 players doing so is very questionable to me.