Artists were encouraged to avoid posting or dropping new music, using their fame and followings to call attention to the anger, grief, and calls for justice among the black community. All about Black Lives Matter: How A Hashtag Defined A Movement ...Nobody seems to understand why individuals started using #BlackOutDay to post the black squares, or when the #blacklivesmatter hashtag got added on. "My Instagram feed today is simply a wall of white people posting black screens," the author Jeanna Kadlec tweeted.