If you check the modlog, you’ll see posts that have been removed by the mods (great job mods, btw!). However, you can still click into the post to see it - benign example here: https://lemmynsfw.com/post/95856
This means that, even though the post is more difficult to find now, the server is still storing and serving the content.
If that content ended up being CSAM, it needs to be completely purged; otherwise, the server ends up distributing it but you need to know the link, which is trivial.
Does Lemmy provide a way for mods to fully remove a post from the server and cache altogether? If not, this feels like a nightmare situation waiting to happen. It’s then also a very scary attack vector.
There’s a “purge post” button, which seems to actually remove content or access to it. I didn’t try it out yet, because there wasn’t a lot of moderation necessary so far, to be honest.