Some communities there are literally calling for the annihilation of Ukraine
https://programming.dev/comment/1999097
edit: Since people are either willfully or otherwose are missing my point, this is a pro-russia, pro-fascist hate group, therefore we shouldn't give them the platform to spread their shit. this is not about me seeing their community or then causing issues accross other communities, it's about de-platforming fascists.
Honestly I think the main reason we haven't seen this is because the core devs are also the admins of lemmygrad, and they can predict how most users would use that feature lol
That said, I totally agree, it's a win both for user agency, and avoiding needless defederation at the instance level