I was just trying to come up with a scenario involving an obligatory ack (but not one in response to someone literally requesting a response every time), as a way of showing that while an ack is not typically obligatory, theoretically there could be a counter examples in the form of the ack-seeker twiddling their thumbs until ack, so to speak. I think you're right that these hypothetical kids would find it infuriating, and such protocol would work better if every ack-seeking message actually had a question ("11pm, ok?") making it explicit. It's just weird to pose a question if the answer is the same 100% of the time, and the only variable is timely receipt. How about this: "11pm, lmk" -- but the suffix is wasted keystrokes whatever it is.