shadow ban people from displaying on their app / site or in their "trending" section.
Discussion
The Nostr protocol is optimized for circumventing censorship. If a relay censors content, users can switch to other relays. For this reason people generally use multiple relays simultaneously.
Stopping a particular party from receiving content is antithetical to Nostr’s design and ethos. So, to answer your original question, no, I don’t think there’s a practical way to prevent specific relays from receiving one’s notes.