I'm like the Japanese soldier who kept fighting into the 1970s on this, but actually signalling is about taking costly action. When people call something virtue signalling what they usually mean is that it's cheap talk, but this is wrong. The whole point of signalling is that it's costly. A more correct application of virtue signalling would be something like those people who contort their lives to genuinely try to produce zero garbage. This is a truly costly action, but it is signalling in the sense that it is more about showing that one cares by being effortful than actually doing something effectual.