Check the modlog for proof, a discussion post about moving this instance to an instance that shan’t be named now got removed for “linking to instance featuring pedo content”.
Ironically that exact possibility was reason for the discussion in the first place so seeing it happen this quickly is a bit funny.
Not sure how best to go about linking to said instance since it seems to get your content removed. DM’s would be the only solution I guess but not sure if those are checked as well.
I highly doubt anyone is actively fucking with the /c here (other than the admins). I’d simply suspect missing metadata or some shit before assuming someone is somehow covertly sabotaging multiple open content discovery services for the fediverse.
The source code for lemmyverse is public so there’s no need to just speculate. I haven’t checked myself but I highly doubt anime@lemmy.ml is somehow getting filtered out of the search results. Imo it’s mich more likely that the community is just the victim of some bug. Maybe check again in a few days, I know lemmyverse had issues with communities disappearing when they couldn’t be reached during the listing updates.