This has happened before, and once it was very funny. The chair told Serena they were going to deduct a point if Richard kept coaching, and Serena's quite audiable response was "What do you want me to do? I'm trying not to listen to him."
Even members of the crowd laughed.
There's an easy solution to this. Tell everybody that if the chair umpires sees it coahcing, the person doing the signaling will be politely escorted form the stadium. Somebody will try to get over, they'll get nailed, and that'll be that. It's not a big deal, except the WTA won't enforce the rule.
Proud to be an American
Not blind. Not uninformed. We are party to atrocities. But the response of the world after 9/11 is worth noting. Even our most dire enemies offered aid. We should all be so lucky.