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.

Like @neshura@bookwormstory.social said, those sites have instances drop on and off the rankings all the time. I had been checking lemmyverse quite frequently over the past couple months...for no reason I am going to mention in this thread...and instances will disappear and reappear every couple days. The ml instance in particular was prone to that. No foul play going on, just typical software flakiness.