On #rude boards like /b/, /v/, and /qa/, "here's your (You)" is used to bully the posted that is being replied to. But on [s4s], if added after a post number, it means that the message was addressed to (You) specifically ;^)
Insert the post number after double implication symbols, just as if you were replying to somebody. Now, on the same line as the post number, press space and add a "(You)". The (You) will show up even for people without [s4s] Interface, but for those that do have it, it may show a double (You) (dubs, nice). You can also add (OP) after (You) if the poster is also the OP of the thread.