"I'm the kind that uses people. I don't want to use you. Ever. Don't let me. Not you." (1.4.116)
Keating's desperate tone really comes out here in his extremely short sentences and his repetition. He's so worried about using Katie that he can barely get the words out.
But she knew when she pronounced the "yes" that she had waited for this and that she would shatter it if she were too happy. (1.6.101)
We don't get a lot of insight into Katie's feelings for Keating, but here we get to go beneath her normally calm demeanor and see just how nervous she is in regards to Keating. She's scared to show too much emotion, lest she "shatter" or ruin things.
There were moments when something rose within him, not a thought nor a feeling, but a wave of some physical violence, and then he wanted to stop, to lean back, to feel the reality of his person heightened by the frame of steel that rose dimly about the bright, outstanding existence of his body as its center. (1.11.129)
This book deals with a lot of different kinds of love, and one of the most profound is Roark's love for his work. The diction and imagery here is very physical, as if Roark's work is a spiritual—as well as something of a sexual—experience.
"Dominique! Haven' you ever been in love at all? Not even a little? "I haven't. I really wanted to fall in love with you. I thought it would be convenient. [....] But you see? I can't feel anything." (1.14.109)
Dominique's inability to feel things coincides with early descriptions of her as icy and cold. Dominique is very closely associated with ice imagery for a large chunk of the novel.
She thought she had found an aim in life—a sudden, sweeping hatred for that man. (2.1.23)
The novel unites hatred and love together quite often—basically any sort of violent, passionate emotion can fall under the "love" umbrella.
It was strange to be conscious of another person's existence, to feel it was a close, urgent necessity [....] (2.2.122)
This might seem like a throwaway passage, but when the supremely selfish and self-centered Roark is super "aware" of another person, it's a big deal.
"I can't stand it, anything to take you away from it, form their world, from all of them, anything, Roark [....]" (2.8.156)
Dominique is being selfish here, which is a good thing according to Rand's philosophy. But she is also being afraid, and that is not a good thing in this novel.
"Personal love is an act of discrimination, of preference. It is an act of injustice - to very human being on earth whom you rob of the affection arbitrarily granted to another." (2.11.30)
The diction here, with lots of SAT vocabulary words, helps to highlight Toohey's pedantic style. Toohey often speaks like he's leading a classroom discussion, and he also throws out outlandish ideas just to see what people will do.
"I love you Dominique. As selfishly as the fact that I exist." (2.14.126)
That's not the declaration of love most people would imagine, but at least Roark is honest. The fact that he loves Dominique selfishly is a good thing, since it contrasts to Toohey's whole selflessness spiel.
Alvah Scarrett had never hated anything, and so was incapable of love. (3.1.190)
Again, hatred and love are closely linked. It's interesting that hatred becomes a sort of prerequisite for love. Alvah is "incapable" of love until he has hated something. Maybe he should go try flying on the day before Thanksgiving. That might cure him.
"As a matter of fact, the person who loves everybody and feels at home everywhere is the true hater of mankind." (3.4.22)
Being at home everywhere sounds like something Keating would aspire toward…which means it's a bad idea. Loving everyone basically means you don't really love anyone, because love can't be stretched that thin. As Roark says, love is very selfish.
"Do you know what you're actually in love with? Integrity. The impossible." (3.8.26)
Aside from Roark, no one gets Dominique quite like Wynand does. He reveals something of himself whenever he speaks about her, though. Here, he lets us know that he finds integrity "impossible."
"But to get things done, you must love the doing, not the secondary consequences." (4.8.86)
Roark lectures Keating on loving his work and the importance of loving the process of creation, not just the material end results. For the superficial and materialistic Keating, that's a tough lesson.