[Epistemic status: shortly after writing this post, I thought I'd regret it. It was not rated very highly by LW karma, and on outside view, it's the sort of rant I often don't endorse later on. But re-reading it after a few weeks, I think it holds up. I still endorse everything I've written here, with the exception of my suggestion that "virtue signalling" is an appropriate replacement for what most people mean by "signalling".]

I still feel a strong empathy for the post You Can't Signal to Rubes, which called out LessWrong for using the word "signalling" incorrectly. That post got heavily, and rightly, downvoted because it also got the definition wrong. :( But it had a point!

At the time of writing, the current definition of signalling on the LessWrong tag is:

Signaling is behavior whose main purpose is to demonstrate to others that you possess some desirable trait. For example, a bird performing an impressive mating display signals that it is healthy and has good genes.

I'm not even sure I should correct it, because this does seem to summarize the LessWrong consensus on what signalling means. But we already have a term for signalling desirable properties about yourself: virtue signalling! Maybe you'll object that "virtue signalling" isn't quite right. Ok. But, could you find another word? I would prefer for "signalling" to point to the subject of signalling theory, which I understand to be the game theory of communication (often focusing on evolutionary game theory).

Scott Alexander's What Is Signaling, Really? seems to get most things right:

In conclusion, a signal is a method of conveying information among not-necessarily-trustworthy parties by performing an action which is more likely or less costly if the information is true than if it is not true. Because signals are often costly, they can sometimes lead to a depressing waste of resources, but in other cases they may be the only way to believably convey important information.

Although all of his examples are about signalling self-properties, he never stipulates that, instead always using the more general conveying-information definition. He also avoids the signalling is automatically bad pitfall. Instead, he explains that signalling is often unfortunately costly, but is nonetheless a very useful tool.

However, reading it, I'm not sure whether he means to contrast signalling with "mere assertion", or whether h...