As someone who would be likely to get a yellow card at any tournament where that system is used, I’ve got to say, if I was handed one and nobody else around me was getting them, I’d be pretty bloody embarrassed. I think that factor is high enough for most reasonable people that they’re not going to go out of their way to exploit it…and I say that as someone that is very…VERY…bad at containing their emotions.
I about blew out someone’s eardrum next to me when I finished Jericho at our local location a few weeks ago. Was only the third time I’ve managed to do it, so I was understandably exited and the location is loud…my volume was WAY WAY over what I intended, heh. I expect that if I did that at a big tourney, I’d probably get some kind of warning…maybe not a yellow card but definitely a “please don’t do that.”
But hey, on the upside, Iron Man is gone now, BUT I got to finish Jericho one last time. 
One problem with those loud noises isn’t that they are often expletives, but that they are loud. Fine for the guy who just lost his ball. Not so fine for the player four feet away from him who is quietly minding his multi-ball and nearly jumps out of his skin when his neighbour drops an f-bomb at 105 decibels…
I don’t know what the right answer is here. It’s not practical to have every game proceed in isolation just in case that some player shouts out loud and possibly distracts another player at a nearby machine. Pinball isn’t like tennis, where the players have an entire stadium to themselves, so there has to be some tolerance for noise in the environment. At the same time, I would think there is a limit and, beyond some threshold, there should be some penalty.