When you make a message in a thread who else knows you did it? Is there a way of letting everyone else know you put a message there?
If it is a new Thread and they subscribed to that Board beforehand then they will be informed.
If it is a Reply to a Thread and they subscribed beforehand then they are informed.
if they have not requested any notifications then the only way they will know is by the User passing by the Board / Latest Topics and seeing your Post.
JB correct me if I'm like overstepping but I think you do allow someone to bring a post to their attention in their welcome thread right?