A multi-community would be all communities with a certain name, across all instances. It would prevent powermods from being a problem on Lemmy. i think it should be notated with m/<insert name here>, just like communities but with m instead of c.
I like to keep my work-related communities separate from my hobby-related communities. So Python/R/Data/Academia communities would be grouped under “work”, and Gardening/Bread/Crochet/3D printing would be “hobbies”, and then I might want a news group where I can see politics, local news, US news, world news, tech news, etc.
This would be really helpful to me for reducing distractions when I’m actually trying to get information about what’s going on in the (real) world or in my specific corner of the programming world.