...which means that describing an act as "signalling" is basically meaningless, insofar as it fails to ascribe to that act a property that distinguishes it from other acts.
That a proposition has the form "every X is a Y" does not make it uninteresting. For example: All matter is made of atoms. All humans are descended from apes. God made everything. Every prime number is a sum of three squares. Everyone requires oxygen to live. True or false, these are all meaningful, interesting statements. "All acts are acts of signalling" is similarly so.
That said, in most contexts when a behavior is described as "signalling" without further qualification I generally understand the speaker to be referring more specifically to cheap signalling which is reliably treated as though it were a more expensive signal.
Yes, this subtext is present whenever the concept of signalling is introduced (another example of an "all X is Y" which is nevertheless a meaningful observation).
"All acts are acts of signalling" is similarly so.
Not really comparable to matter being made of atoms, though, as "signalling" only establishes a tautology (like all communication is communication).
Another month has passed and here is a new rationality quotes thread. The usual rules are: