Right: I think everyone gets that; but it is that very concept that is irksome, as the entire reason to use chat apps for many people is to NOT have presence-at-keyboard EVER. Like, the answer to "are you there?" is, an hour later, "no", followed by immediately task switching away from the window again. The "no" is honest: I wasn't there when you asked, and I also am not
really there now either. It is akin to trying to obtain synchronous communication with someone by sending them a letter with "hey, you there?" and a month later getting back "yo! what's up!"... you didn't really achieve much other than "this communication mechanism worked once"; and, if you want to do that in a way that makes it clear you
aren't trying to establish synchronous communication--•I am sorry, but I am new to chat: are you actually seeing this message?"--I am more OK playing along.
The goal here--and I think a better way to present it than just trying to say "don't say hello" or trying to point out that someone else is being rude (which is a subjective way of analyzing things that I think people should avoid without empathy)--is in some sense to teach people what asynchronous communication means and how to achieve it, as I honestly don't want to and kind of can't have synchronous communication with anyone whom I don't really really really care about at the level of "a close personal friend or loved one" (and then if you find that rude, I guess you will have to deal with synchronously talking to someone else, at best my assistant, as I just really don't have time to synchronously talk with random people; but that's the problem: I know "hi; you there?" is a trap to try to make me feel bad for not staying synchronous once you pounce on my answer later).