When did acknowledgement of receipt of a message become a commitment to accede to its demands?

I must be a Wallace, because I too think it's alien to form commitments implicitly. I don't even mean the sort of implicit that lacks only a commitment phrase like "I agree"; no, I mean that sort where failure to reject a message is enough to form a commitment.

To be fair to Rands, Wallace could also learn to be a bit more forthcoming with objections, otherwise it becomes a game of 20 Questions to determine which of an infinity of possibilities is blocking a resolution.