You can stop your comments from being sent to specific instances? Client-side filters just hide incoming traffic but AP is still doing its own thing in the background afaik, but do correct me if I'm wrong. At least I couldn't find anything to suggest otherwise, and client-side does kinda imply that it's just a visual alteration on the client's side.
But I was mostly talking about kbin/lemmy, sorry about that. I dont have that much experience with mastodon yet.