If you reply to a post to add someone’s handle to it, to have that person see the post, here is a better way:
Say the post is from user A, and you hit reply. You then get a reply which contains @ A. Many then just add the name of the person they want to see the post, replying with @ A @ B. But that means A is notified, that you have written something for them, which is really not ideal.
So instead, delete the @ A, then write @ B, and hit reply. B gets notified, A is not bothered.
