Hello, I hope you are well. From my experience as a SEA, which I assume this experience is also similar to EA people. Anyone that is around your age or older is called sister or brother, if they are much older then use uncle or aunt. If they are much younger use young sister or brother. It is used in almost all settings especially with people who you don't know their names. For example a waiter comes to take your order at a restaurant, you would say "Sister, I would like a cup of tea".

From what I understand the use of the word sister for a black person is more similar to the word comrade, please correct me on this.

Woaw, I love purging now

Same, I hope we are not getting purged

I didn't think I could get more disappointed than I already was.