“Weighted” is also a very nice sort, that tends to lift up smaller comms.

The common term is “communities” or “comms”, I think.

I would try to look for servers dedicated to the subject you’re interested in and see what communities they have. Keep in mind that there are much fewer users on Lemmy than Reddit, so there might not be a specialized community for a given subject. And if there is, it might be very small/inactive.

They’re real. It’s a combination of them sagging/being broken and being reflected in the perfectly still water.