And all around these neatly lettered words, scribbles had been added by other witches and wizards who had come to see the place where the Boy Who Lived had escaped. Some had merely signed their names in Everlasting Ink; others had carved their initials into the wood, still others had left messages. The most recent of these, shining brightly over sixteen years’ worth of magical graffiti, all said similar things.

Good luck, Harry, wherever you are.
If you read this, Harry, we’re all behind you!
Long live Harry Potter.

“They shouldn’t have written on the sign!” said Hermione, indignant.
But Harry beamed at her.
“It’s brilliant. I’m glad they did.”

Harry Potter and the Deathly Hallows – J. K. Rowling