[persona]

There is a strong counter-argument though, based on the increase of online meetings and screen sharing scenarios... Not everybody always remembers to silence screen notifications while sharing screens.

Which leads to more-than-once-a-week situations of "Hi - full question or comment notification that probably shouldn't be seen by co-worker/boss/client" popping up during the share.

A simple "hello" --wait for answer-- protocol makes it a quick way of checking if it's a good time.