The time wasted isn’t saying hi back. The time wasted is 1. Some nonzero time waiting in case of a prompt reply to the initial hi. 2. Some probably greater ti

The time wasted isn’t saying hi back. The time wasted is 1. Some nonzero time waiting in case of a prompt reply to the initial hi. 2. Some probably greater time waiting for an async response. 3. The time it takes to restore previous mental context and flow. 4. 1-3 again, but with the parties reversed. And, let’s be honest, probably for a longer duration. All time spent to convey approximately zero information.