I think when you put someone in the blacklist not only you should not be able to see anything that they type but they should also be invisible to you and you to them.
Makes people who troll and be nasty just... vanish when you put them onto the blacklist.
For example had a guy a few days ago spent over 3 hours in Limsa begging people for gil running around naked standing on top of players who were just trying to chill out and chat to friends. Sure adding him to blacklist meant you couldn't see him beg but it didn't stop him from being toxic in other ways.
If both the person you put on the couldn't see you anymore and you couldn't see them it would really punish those who are toxic by literally making it that if they annoy and upset enough people they will be walking into for example Limsa and seeing... No one. GL trying to be toxic and nasty when you can't see anyone and no one can see you or read anything you type.