[upofadown]

If it bugs you just don't respond to the hello. If someone complains just say you were waiting for the actual content (no one just says hello on chat for no reason). You assumed that the hello was just to warn you that something longer was being typed and that you shouldn't immediately leave.

The nice feature of this approach is that you can immediately leave if you know that you really don't want to deal with whatever it is that is coming and can legitimately say you never saw it.

[Jach]

Yup. I ignore a lot of "hey"s, if you respond then it just incentivizes more later. No one has complained but I'd just complain back about their inefficiency. If it's an emergency, they can call me twice.