I didn't read the whole game, but that's not a bug. The player was just whispering to someone else.
There was no crier in the game, so it seems it doesn't depend on crier's existence.
Though I wonder if it would still work if crier DID exist... if the user is injecting code, probably.
Also, it's peculiar to me that it says "Someone whispers" instead of "Someone cries out".
That's what invis messages look like...
