For people who don't get the "signaling device" thing, think of it like this. I'm starting a cult that has two core beliefs:
1) Dogs are awesome.
2) Humans have ESP, but electricity interferes with it. If we stopped using electricity, we would all be able to communicate telepathically.
There are a bunch of people in my cult, but I think some of them are just poseurs. I need a way of differentiating between the true believers and the ones who are just playing along. One way to accomplish this is to get people to talk about their cult beliefs in public, but you can see where it doesn't do me much good to emphasize point (1). Suppose I tell people "You need to get out there and talk more about how awesome dogs are -- I'm watching, and I'm judging your loyalty based on how pro-dog you are in public." How does that accomplish anything? Everybody thinks dogs are awesome. The poseurs in my cult can go on and on about how great dogs are and nobody will judge them negatively in any way, so of course they'll repeat that talking point. It's costless and therefore worthless for my purposes.
Point (2) is great though. If I demand that my cult members go on anti-electricity rants in public, the poseurs are unlikely to go along. It's an insane belief, and saying crazy stuff about electricity in public will tend to make people think you're nuts, and ordinary people will be reluctant to pay that reputational price. But the true believers don't mind paying that price. They see it as a worthwhile tradeoff in exchange for building their status inside the cult. (1) doesn't do a good job of signaling loyalty to the group because (1) is widely accepted and therefore costless to affirm. (2) does a great job of signaling loyalty because (2) widely unaccepted and therefore costly to affirm. Good signals have to be costly.