If you have millions of people on a social network, and you go looking for toxic shit there, you will find it.
Well, on Mastodon, you might not because by default it doesn’t have a useful text search feature. If you’re on a server running a modified version, or something else with decent text search, you might. My self-hosted server was on a relay that briefly pulled in content from a famously toxic server. At first, I didn’t see it because I didn’t follow those accounts, but later, I added an improved search feature and tried searching for some terms of abuse. I did find a few absolutely vile posts.
Bluesky has had a working search from early on. Turning off some of the default moderation filters and searching for terms of abuse does, in fact find people using terms of abuse.
It’s the largest by far, with five times the monthly active population of #2. One of the main things people want out of federated systems is decentralization, and having one huge dominant server goes against that goal.
I should note .world wasn’t the biggest when I signed up. I picked it because mastodon.world was a known quantity, which led me to believe the same team would run a stable server.