The theme of separation is in full swing in this chapter. Harry himself notes that things are not as rosy and cheerful as he’d hoped upon returning to Hogwarts. He thinks:
Between the absence of Hagrid and the presence of those dragonish horses, he had felt that his return to Hogwarts, so long anticipated, was full of unexpected surprises, like jarring notes in a familiar song.
And remember Rowling’s use of the drought motif from the first chapter? In the chapter we just read she uses the weather as a mirror for Harry’s unsettled mood. She writes:
The train rattled onwards, speeding them out into open country. It was an odd, unsettled sort of day; one moment the carriage was full of sunlight and the next they were passing beneath ominously grey clouds.
The weather remained undecided as they travelled further and further north. Rain spattered the windows in a half-hearted way, then the sun put in a feeble appearance before clouds drifted over it once more.
Now in chapter eleven, Harry find himself connecting with Luna in an unexpected and rather intimate way: she is the only one who sees the Thestrals besides him. As she famously puts it, “’Don’t worry. You’re just as sane as I am.”
For Harry, this connection to the one everyone thinks of as an oddball is unpleasant. It doesn’t fit with the image he has been building up of himself over the last year or two. It doesn’t fit with the one who could outfly a dragon or who managed to catch the Snitch and win Quidditch matches. But identifying with Luna, who personifies faith, love, and acceptance in the stories, is exactly what he needs to do in order to become the true Chosen One.
Harry won’t begin to realize this until the end of the book, when he meets Luna in the corridor during the Leaving Feast. Harry has been trying desperately to find a way to contact his dead godfather, from talking into a magic mirror to questioning Nearly-Headless Nick about ghosts. Luna, who is calmly posting notices for people to return her stolen belongings, immediately brings up the death of Sirius and Harry realizes to his surprise that it doesn’t bother him as it had with everyone else. He realizes why. “He had just remembered that she, too, could see Thestrals.”
This shared, deep understanding about life and death, about belonging and loss, connects him to the larger truth that Voldemort never grasped: that there are worse things than death. It is this deep understanding and acceptance, personified by Luna’s calm belief that not only would she see her dead mother again but also would recover all her stolen belongings, that is the foundation for the new Harry we will meet in books six and seven.