So, for the example of people seeming to say that costless signaling is an effective way to influence the behavior of rational agents, I would direct you to the comment to which I was replying. Tim wrote:

Well you don't want to signal that you give in to extortion. That would just increase the chances of people attempting extortion against you. Better to signal that you are on a vendetta to stamp out extortion - at your personal expense!!!

I interpreted that as advocating costless signaling as a way of influencing the behavior of would-be extortionists.

You seem to be the only one talking about "costless signaling" here.