Nico actually had one of the cutest laughs ever. But, unfortunately, he tried his best to hide it. Which meant that he normally stayed away from anything entertaining, resulting in him being gloomy all the time.
Hazel changed that. She started dragging Nico to games of truth or dare, and parties thrown by the other cabins. And, eventually, the son of Hades stopped trying to hide it. He'd have fun with his friends and laugh until his stomach hurt.
Ever so slowly, Nico di Angelo became accepted more and more at Camp Half Blood. And when the big secret came out, no one was bothered by it.
AN: Yes, I'm talking about the House of Hades secret. I figured if Nico becomes more accepted at Camp, the demigods wouldn't be very bothered by it, and they'd support him.