I made a diagram to help you understand how the different timelines/columns work:

https://techn.ical.ist/assets/help.svg https://techn.ical.ist/media/zhoMEHOzhT2r6zlz034

@vhf Nice. A related feature: profiles which don't generate sufficient interest to be followed ... only "pollute" their local Instance. The concept of distance or reach of a given profile or post might be useful to consider as a microblogging service scales. You don't /want/ absolutely /everything/ to appear /everywhere/.