Filtering Broadcasts:

Every player would have a set of options much like chat filters where you can set yourself up to receive or send broadcasts to and from certain groups of users. You can set yourself up to broadcast to groups such as friends, individual linkshells, as well as free company. Furthermore you could choose to restrict your broadcasts so they don't get sent to specific users (i.e. you don't like playing with one person in a certain linkshell, you will not send that person a message when you enter the duty finder).

Likewise, you would have those same options for who you receive duty finder broadcasts. You can set it up to only recieve broadcasts from friends, linkshells, free company, specific users etc. as well as block broadcasts from specific users.

Once these options are set, duty finder notifications can be set as a chat filter just like every other kind of text you receive in game.