No. For the sender, yeah, time and effort is the same (or even less, as it saves hitting carriage return/newline once), which makes it more infuriating. Becaus

No. For the sender, yeah, time and effort is the same (or even less, as it saves hitting carriage return/newline once), which makes it more infuriating. Because for the recipient there is an extra latency of several seconds after the useless "hi" message during which he cannot sensibly continue with his current task (switching cost), but cannot quickly resolve the interrupt either, because it is unclear what the issue is.