It's an interesting thought. Though the greeting of the day in real life is more just meant as a courtesy between soldiers usually when just passing by. Here, you don't exactly pass by anyone to enable you to give the greeting of the day. When entering a ranking officer's channel you usually address him/her by their rank and name and wait for them to respond, usually asking what you need. When a ranking officer enters your channel, it's important to cease all conversation and await for any possible orders or instruction. I'm not quoting any standards or documents, I'm just kind of telling you how it is from what I've seen. There's probably more to be said in greater detail, but that's just the general gist of it.
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