If you haven’t already, you’ll probably want to read this study on CSAM from Standford which discusses the lack of automated tooling (and how PhotoDNA isn’t really equipped to handle thousands of Mastodon servers).
Some other Stanford researchers (including Alex Stamos, former CSO for Facebook) just put out this piece on Mastodon moderation too, which is worth a look.
When considering moderation, it’s also worth thinking about the role of defederation. From the first report, the CSAM on Mastodon sounds like it’s mostly on Japanese servers, and most western-oriented servers have defederated from them over that, so the content won’t travel across the network. I know that if that appeared on my server, the admins would probably defederate until the source cleaned up their act.
Laurens Hof posted a roundup of algorithmic Mastodon clients that can highlight interesting stuff from a server’s federated feed:
Using those is a good way to find interesting stuff and people to follow.