For me, personally, John and Harold are a pair of Aces.
I know we saw John in a relationship with Jessica but I like to think they were Intimate but not Physical. They did their cuddling and drinking and falling in love and everything was nice. John never dreamed he'd find anyone he loved that wouldn't ask him for more than he could give and Jessica was perfect.
But she didn't last. And then Kara. Kara was the opposite of perfect. John was indeed Physical with her. Let her touch him though it made him ill. All part of the job, she liked to whisper to him in the darkness where he hated himself as much as he hated her.
And then came Harold. Sweet little Finch still in love with Nathan's ghost. The spirit of the man he was never even Intimate with, though he had loved him so. Harold cares about John, loves him, in his own way. And when it becomes a love they share, romantic and craving to become Intimate, John is prepared to make consessions if Harold does desire it. Except he doesn't. Harold tucks in against him and doesn't ask for kisses or the kinds of touches John doesn't like. He just nuzzles in and lets John put his arms around his back and it's not Jessica but it's perfect.