Hello, here's a question as a fellow Sherlockian and Johnlockian, what do you think of the scene nearly at the end of TAB, where John says: "I'm taking Mary home" but then Mary looks at him strangely and he corrects with "Mary is taking me home"?

Hello, thanks for your question! I’m going to quote a bit from @heimishtheidealhusband​‘s “The Graveyard Domestic” meta- there’s a lot going on in both subtext and text during that entire scene, but I’ll pick out the part that talks about the “I’m taking Mary home” exchange. Basically, what you need to remember is that the whole graveyard scenario is partly Sherlock playing out his worst fears and insecurities- John now disparagingly calls him an addict, will only stay with Sherlock because of “the Work” and will abandon him. Or, as @heimishtheidealhusband explains:

John: I’m taking Mary home.

Mary: You’re what?

John: Mary’s taking me home.

Mary: Better.

And with that, John and Mary depart. Welcome again to the “worst fears” portion of Sherlock’s gay Victorian fever dream. Sherlock chose The Work over John, and John didn’t wait for him – instead he left with Mary. No, scratch that, even worse, he let Mary take him home. Because for Sherlock, assassin Mary being in control of that relationship is pretty much the worst case scenario, hmm?

As far as I see it, this is Sherlock’s mind recognising that Mary and John’s marriage is far from a partnership of equals-Mary is in full control. Considering that this is all in Sherlock’s head, even his imagined version of Mary undermines him, hence her quick double take when John initially says “I’m taking Mary home.” She can even ‘correct’ what is being said inside Sherlock’s head: Excuse me? John’s taking me home? Oh sunshine, have you got another thing coming…