Differences in instance-level topical focus and moderation philosophy, for one. Also physical location and “vibe”.
There are a certain set of bigoted and/or extremist instances that I would judge an instance for not defederating from. There’s a reason I’ve stuck with .world even through some turbulence. Some heinous shit shouldn’t be tolerated by anyone.
the smell of heavily chlorinated water. i used to spend a heck of a lot of time at the pool when i was a kid, and where i live now there aren’t nearly as many pools, so it’s not something encountered often anymore.