When does one stop being Dummy?
Last evening, I (South) was dummy and observed East revoke by failing to follow to a Diamond lead at trick 4, actually discarding a Club. Even though she played several more Diamonds during subsequent tricks, no-one commented on it. I know I wasn't allowed to comment and, sure enough, at the end, everyone rapidly scooped up their cards, shuffled them and put them back into the board before I had chance to say "what about the revoke?".
At what precise point do I cease to be dummy and thus become eligible to speak?