i didn't want to put this on op's post because i’m sure they were mostly joking and i'm not trying to call them out or anything, but it just made me think about the queer subtext surrounding jim and how that often gets overlooked in favour of the 'kirk drift' narrative. so here are some of my thoughts on that:
Spock is very easy to read as queer-coded, not only are there multiple moments in the show where he explicitly isn't attracted to women (at least in a human context), but there's also the factor of his Human/Vulcan heritage which makes him feel like he must repress his emotions. This has queer subtext in the general sense that it can be an allegory for otherness/queerness, but also literally because a lot of the feelings that we see him repressing are feelings for Jim.
In Jim's case it can be more subtle. Most of the subtext revolves around duty and, subsequently, loneliness.
In ‘The Naked Time’, the same scene in which Spock says “Jim, when I feel friendship for you, I’m ashamed” (LOVE MANKIND) Jim starts to talk about the ways he isn’t permitted to love freely because of his duty as captain:
KIRK: I've got it, the disease. Love. You're better off without it, and I'm better off without mine. This vessel, I give, she takes. She won't permit me my life. I've got to live hers.
Then, at the end of the episode:
SPOCK: […] We can go back in time, to any planet, any era.
KIRK: We may risk it someday, Mister Spock.
i.e. They may risk loving, someday.
This brings to mind this quote from Gene Roddenberry:
RODDENBERRY: Yes there’s certainly some of that [closeness of friendship, feeling that they would die for one another], certainly with love overtones. Deep love. The only difference being from the Greek ideal, we never suggested physical love between the two in the series. We certainly had the feeling that the affection was sufficient for that, if that were the particular style of the 23rd century.
Homosexuality was illegal in the US when the show was made, and was heavily censored in media. Homosexuality in the US military, which is the specific focus of Jim’s queer subtext here, has only been legal for the past decade. Both within and without the story, they look forward to a future where they can love openly and freely.
In ‘The Menagerie’, when Spock steals the Enterprise to take his former captain, Pike, to Talos IV, Jim is faced with sentencing him to death for mutiny:
KIRK: And in all the years of my service, this is the most painful moment I've ever faced.
Later during the trial, Commodore Mendez, in a hostile tone, accuses him of being biased towards Spock:
MENDEZ: You have that right, Captain, but just because the prisoner is your First Officer and your personal friend-
Kirk has to defend himself against being emotionally compromised due to their relationship. Would Mendez be so accusatory if they weren’t so close? In the TMP novelisation, written by Gene Roddenberry, we learn that there are rumours about Kirk and Spock’s relationship. In the context of a trial where Spock may be sentenced to death for (in act of what Kirk describes as ‘flagrant emotionalism’) taking Pike to Talos IV, it’s not a stretch to suggest that Mendez is accusing them of something more serious. We don’t know if ‘that is the particular style of the 23rd century’ (i.e. if homosexuality is legal/accepted then), so perhaps it is just subtext of the era it was written, but this always strikes me as the underlying threat in Mendez’ words.
In ‘The Apple’, they visit a ‘paradise’ where the people are not free to love and only live to serve a machine. When they meet the people they find out that love is forbidden by Vaal, then each male crew member is given a bracelet made of flowers. (Yeoman Landon is given a flower to wear in her hair.) Spock comments that it makes him uncomfortable. In the next scene, we see both Kirk and Spock, and only them, remove their bracelets. Perhaps a rejection of their way of life? A silent protest for freedom to love?
The episode ‘This Side of Paradise’ also shows how Kirk feels tied to duty, at the expense of his happiness and love.
(After Kirk is infected by the spores.)
KIRK: I've joined you. I understand now.
SPOCK: Wonderful, Jim.
[...]
(He packs a suitcase with a smile on his face, then goes to the safe and gets out his medals. He loses the smile.)
---
SPOCK: I have a responsibility to this ship, to that man on the Bridge. I am what I am, Leila, and if there are self-made purgatories, then we all have to live in them. Mine can be no worse than someone else's.
---
MCCOY: Well, that's the second time man's been thrown out of paradise.
KIRK: No, no, Bones. This time we walked out on our own. Maybe we weren't meant for paradise. Maybe we were meant to fight our way through. Struggle, claw our way up, scratch for every inch of the way. Maybe we can't stroll to the music of the lute. We must march to the sound of drums.
‘March to the sound of drums’ is a very clear reference to the military. The emotional outburst that breaks Jim free of the spores’ influence comes from looking at his medals and being reminded of his duty. He loves his ship, and yet as long as he has her, he can never be free. Similar to Spock, this is his self-made purgatory.
Kirk and Spock were written as two halves of a whole, and Spock is only one half of the K/S equation. While Spock is fighting his emotions, Jim is struggling against his duty. He often faces the choice between Spock and his career.
When Kirk is put through the neural neutraliser in ‘Dagger of the Mind’, Adams includes sacrificing your career and reputation in the ‘symptoms’ of being madly in love.
ADAMS: You're madly in love with Helen, Captain. You'd lie, cheat, steal for her, sacrifice your career, your reputation.
In 'Amok Time', when Spock is forced to return to Vulcan to ‘take a wife’ or die, Jim sacrifices his career, and later almost his life, to get him there.
KIRK: I can't let Spock die, can I, Bones? And he will if we go to Altair. I owe him my life a dozen times over. Isn't that worth a career? He's my friend. Bridge. Navigation.
---
KIRK: Bones. He's my first officer and my friend. I disregarded Starfleet orders to bring him here.
This is paralleled in 'Star Trek III: The Search for Spock', when Jim risks his career – literally blowing up the Enterprise – for a chance to bring Spock back to life.
KIRK: What I have done, ...I had to do.
SAREK: But at what cost? Your ship. Your son.
KIRK: If I hadn't tried, ...the cost would have been my soul.
As for Kirk’s reputation as a womaniser, many people have written about the ‘Kirk Drift’. Out of 20 kisses in 80 episodes, only three were fully consensual and had no ulterior motive: Areel Shaw in ‘Court Martial’, Edith Keeler in ‘The City on the Edge of Forever’, and Rayna in ‘Requiem for Methuselah’. When he isn’t being coerced, and has full control over his mind, he is usually trying to use his sexuality to escape capture. (Which is a whole other conversation.) Very rarely is he doing it for only pleasure, and yet he gained the reputation as a ladies’ man. In contrast, if you look at the text, Kirk is incredibly lonely.
In ‘Metamorphosis’, Jim tries to convince the Companion to release Cochrane:
KIRK: Companion, do you love the man?
COMPANION: I do not understand.
KIRK: Is he important to you, more important than anything? Is he as though he were a part of you?
COMPANION: He is part of me. The man must continue.
KIRK: He will not continue. He will cease to exist. By your feeling for him, you are condemning him to an existence he will find unbearable. He will cease to exist.
[…]
KIRK: But you can't really love him. You haven't the slightest knowledge of love, the total union of two people. You are the Companion. He is the man. You are two different things. You can't join. You can't love. You may keep him here forever, but you will always be separate, apart from him.
[…]
MCCOY: What did you hope to gain by that, Jim?
KIRK: Try to convince her of the hopelessness of it. Love sometimes expresses itself in sacrifice. I thought maybe if she loved him, she'd let him go.
I had always read this scene as a parallel to Spock, where Spock is the Companion and Jim is the man. However if you consider Jim as the Companion and Spock as the man, it makes even more sense. Jim can keep Spock with him forever as his First Officer, but in doing that they can never be together. By loving Spock in this way, a way in which he finds unbearable, it’s destroying him. This parallel is made again in ‘Requiem for Methuselah’, through the android Rayna who is pointedly very similar to Spock:
SPOCK: [Rayna] loved you, Captain. [...] There was not enough time for her to adjust to the awful power and contradictions of her new-found emotions. She could not bear to hurt either of you. The joys of love made her human, and the agonies of love destroyed her.
We know that eventually Spock leaves to complete the Kolinahr to purge himself of his emotions.
'Star Trek: The Motion Picture' is mostly about Spock’s realisation that without his emotions, he is barren and cold, there is no mystery and no beauty. However, once again, we see Jim struggling with loneliness. After the five year mission, he was pressured into a promotion as Admiral, grounding him on Earth, and also manipulated into a contractual marriage. Although he has managed to retake command of the Enterprise, Jim is still unhappy and lonely. Throughout the film, he is constantly reaching out, and as Spock has this profound epiphany, they hold onto each other.
'This simple feeling' is two hands searching for each other. T'hy'la, by nature, cannot be one sided, it is shared between them.