Sorry I misunderstood your comment:
Nightdev isn’t responsible for how the chat works on streaming platforms, there’s no way for a message to be sent only to viewers without it being sent to the broadcaster as well. The only solution to your problem is if the people working on that Playstation 5 feature include a user blacklist.
Some tools, like Kapchat, allow to blacklist a user, but those tools are made to have a chat displayed in your broadcast, not for text-to-speech.