So I had a look at how Sherlock and John describe each other, leaving out terms like “idiot” and “annoying dick” (even if they are not used in an insulting way) and concentrating on positive descriptions. I came up with this list which surely is not comprehensive but should provide a sufficient basis:
John about Sherlock:
my best friend
the most human … human being
you were the best man
You were the best and the wisest man that I have ever known.”
“’Course you’re my best friend.”
Sherlock about John:
This is my friend, John Watson.
My friend John Watson
the bravest and kindest and wisest human being I have ever had the good fortune of knowing
one feature, and only one feature, of interest in the whole of this baffling case, and quite frankly it was the usual. John Watson.
Then I had look at how John who is supposed to love Mary talks about her. Guess what? I could not find a single positive word or expression. Nothing but negative or neutral terms and I looked at all the episodes. This is what I found:
my lying wife
the woman who’s carrying my child who has lied to me since the day I met her
my pregnant wife
Not a single term of endearment. Sherlock at least once calls her “clever” whereas for John Mary seems merely reduced to her functions: wife, assassin, client. The language is quite telling, if you ask me.
Sherlock, John, and Mary - A Matter of Give and Take
JOHN: John Hamish Watson – just if you were looking for baby names.
JOHN: I choose the baby’s name. MARY: Not a chance.
SHERLOCK: William Sherlock Scott Holmes. (…) That’s the whole of it – if you’re looking for baby names.
This is such wonderful example of why Sherlock and John belong together and John and Mary don’t.
Both John and Sherlock are offering their full names to each other. And this is a strong contrast to Mary who never gives anyone her real name.
Of course there is the nearly identical wording as well.
And if you compare this with Mary’s snappish remark when John - who has been treated cruelly by her - wants to choose the baby’s name, it becomes clear that Mary is demanding and taking what she thinks is her right while John and Sherlock are offering and giving.
This is one of Mary’s functions in the narrative: emphasising the ultimately selfless love between Sherlock and John by setting it off against her selfishness.
And the use of full names is reminiscent of wedding vows as well. So in a way we get wedding vows for Sherlock and John while the “real” wedding between John and Mary is never shown. But then Mary Elizabeth Morstan was never a real name.
Charlie was excited to finally be back from winter break. Being back at Hogwarts meant getting to spend more time with his girlfriend, Mary. Sure, he’d seen her over break, but it wasn’t the same. They had their own family parties and things to attend, so they weren’t together nearly as often as he would have liked. Even when they were together, if she was visiting chances were his siblings were around to annoy him and give them no alone time. And, even though Marlene had known for a while now, they were still both hesitate with being couple-y around her.
Once they got back to Hogwarts on the train, everyone had a welcome back feast in the Great Hall and then were off for the night. He had waited for Mary to leave the Hall and go up to his dorm, which is where they now sat. She was at one end of his bed while he was at the other, going over his notes and making sure all of his assignments were done for class starting up again the next day. Even while they weren’t talking much, it was nice to just be together.