Disclaimer: I do not own Trip, Malcolm or Jon.
This was inspired by a heartbreakingly similar situation that I'm watching two of my friends go through right now. Comparing how they were a year ago to how they are now is like looking at season 1 Trip/Archer interactions compared to season 3 or 4. It's terrible; they're just not best friends anymore, and it'll never be the same for any of us.
Surrogate
Trip has breakfast with Malcolm, and lunch, and dinner. He goes out of his way to make sure their shifts are the same. Yet whenever he's invited to eat in the captain's mess, he's got something that just has to be done.
They never came out and said, face to face. They never admitted it in front of each other. But Trip and Jon just aren't friends anymore, and Malcolm knows that. Everyone knows that.
Trip does with Malcolm what he used to do with Jon; they watch the same movies, tell the same jokes.
Malcolm feels like a surrogate.