True words for 1:n communication. For 1:1 communication it's a different thing though. I really prefer people to warn me before dropping a bomb
Why? These "hi" or "are you there" or "can I ask a question" are useless to me. Also in the reverse role I find it useful to just type up my whole problem. Sometimes in the middle of typing it all up I will figure out a good solution and then just not send the message. Even if the person is not there to help you, you can always copy paste your message to someone else.
(With dropping a bomb I also mean something like a larger/tedious amount of work)