I love how, canonically, Nicolas is just as bitter and mean about things he loves, and characters like Lestat have to really look to see him drop the sarcasm. (Bold/emphasis mine)
This is how he describes Paris in the book:
"Now, I shall tell you everything you want to know about Paris," he said agreeably, waiting for me to sit first. "Yes, I did go to the university." He made a little sneer as if it had all been contemptible. "And I did study with Mozart, who would have told me I was hopeless if he hadn't needed pupils. Now where do you want me to begin? The stench of the city, or the infernal noise of it? The hungry crowds that surround you everywhere? The thieves in every alley ready to cut your throat?"
His smile was very different from his tone, his manner open and appealing...Soon he was describing all of Paris and he'd forgotten to be cynical..."I'll tell you," he said finally, "it all sounds a hell of a lot better in this room than it really is."
All summarized very neatly by the phrase
But no matter how deadening was this sarcasm of his, a great energy poured out of him, an irrepressible passion
The key to their relationship is that Lestat sees through the sarcasm to the passion, and he realizes that Nicolas likes his idealism.
"And you'll find Paris is a miserable hellhole," he said. "Where they break the bones of thieves on the wheel for the vulgar crowds in the place de Greve."
"No," I said. "I'll see a splendid city where great ideas are born in the minds of the populace, ideas that go forth to illuminate the darkened comers of this world."
"Ah, you are a dreamer!" he said, but he was delighted
But it's not just Paris. Earlier Nicolas dismissed his music and his talent as "hopeless". But then he plays for Lestat for the first time, and Lestat is moved by the passion of his playing. and Nicolas, again, loses the edge.
He sat next to me, hugging me and asking me why I was crying, and though I couldn't tell him, I could see that he was overwhelmed that his music had produced this effect. There was no sarcasm or bitterness in him now.
When Lestat professes an earnest interest in acting, Nicolas shuts it down with undercutting the romance again. But Lestat points out Nicolas does believe in music and the arts himself.
"Actors and actresses make magic," I said. "They make things happen on the stage; they invent; they create."
"Wait until you see the sweat streaming down their painted faces in the glare of the footlights," he answered.
"Ah, there you go again," I said. "And you, the one who gave up everything to play the violin."
He got terribly serious suddenly, looking off as if he were weary of his own struggles.
"That I did," he confessed.
Even when Nicolas is actively encouraging Lestat to undertake the journey to Paris, he can't help but do it in an angry way.
I loved this change in "our conversation"! I loved seeing him believe we could do it. All his cynicism had vanished, even though he did throw in the word "spite" every ten words or so.
Nicolas teaching Lestat to read, or reading his parts to him, could be a sweet scene. And it is based in genuine care! But Nicolas shows his genuine care while shouting at Lestat.
Nicolas had taught me the part, bawling me out constantly for not learning to read. And by the fourth performance, the playwright had written extra lines for me.
Truly, tsundere behavior. It honestly reminds me of those jokes about people in Boston/the Northeast who will be kind but not nice. The kind of people who go "Jesus, what the fuck is wrong with you, are you stupid or something?" even as they're in the middle of giving you directions or fixing your flat tire. Nicolas has a tendency to be bitter and sarcastic about 100% of the time. And if he truly loves something, he'll still talk angry and cynical about it, but his actions will reflect that love and enthusiasm.