@gwenthefops
The key difference is that communities outside of microblogging require the intent to switch contexts. In case of the gym, it's the act of entering the building. Online, it's the act of opening a forum in the browser. In chat rooms, it's the act of switching rooms. There's always clear separation at this current moment, and the group members are aware of this as a subtext
Microblogging isn't like this, even with the existence of local posting because by and large, you're still always confronted with a mixture of global and local since it's too easy to switch between them on a whim. This deprives everyone of this deliberate context switching mechanism that otherwise permeates our lives, and this leads to all kinds of weirdness. I have written about it here: volpeon.ink/notebook/microblogging-misdesign/