It still works as a signal, because (1) signing a comment requires some extra effort, and (2) it is harder to retract a comment that has been signed (since the signature remains valid proof of authorship even if the original comment is edited or deleted). A little bit of real cost and utility goes a long way.
Telling people what you’re trying to signal is a way to make them take your signaling less seriously.
It still works as a signal, because (1) signing a comment requires some extra effort, and (2) it is harder to retract a comment that has been signed (since the signature remains valid proof of authorship even if the original comment is edited or deleted). A little bit of real cost and utility goes a long way.
But PGP’s security and quality pretty much make up for that loss in signaling seriousness, don’t you think?
Unless you’re signalling that you know about signalling including acknowledging your own signalling. :)