A) Want to know when they've been online the last time/what time they usually come online
B) Wait for them to come online but not start a conversation
C) Wait for them to go offline before going offline yourself?
Not something I'm doing or would do, I'm just an observer and trying to understand what goes through their head. Not judging anyone, just finding it fascinating and want to figure out what people get from this kind of behavior / why they would act like this :)