I often ignore people's status, but it goes both ways... if somebody is online but doesn't reply I'll just assume they're away or busy and I won't keep bugging them with "hey are you there?" or "why aren't you replying".
If somebody is busy or away I'll make sure I put what I want to say in the first message... if they don't reply to that they're probably really busy or away... if they do reply, fine let's have a conversation.
But i do have conversations starting with this no matter what status I'm in: "Hi! hey. What's up? nm, you? Same." If you start a conversation with someone, make sure you actually have something to say
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That's why I almost never start convos with anyone, I never know what to say and I don't wanna be boring.