Hi hi,
short and sweet: Currently if player A blocks player B, then the messages from player B will no longer deliver. However, player A can still continue to send player B messages even after the blocking. Player B would have to explicitly block player A to not get their messages anymore.
This could cause weird situations where someone gets blocked, keeps receiving messages from the player that blocked them, tries to reply, but obviously their messages don't deliver because they themselves are blocked. Without a way of knowing for sure if they are blocked, this could well drive someone insane.
My proposal: If palyer A blocks player B, then not only do player B's messages to player A no longer go through, but vice versa, messages from palyer A to player B should also not send anymore.
Edit to add: In this case, if player A blocked player B and tries to reach out, the game could also give a little error pop up saying you can't message people you have blocked. Player A should technically already know they have player B blocked, so there is no secret information revealed in this case, the error would just remind them to unblock the person if they do want to reach out.