when montag and clarisse arrive at her house, what does montag find odd about the house?

Montag finds it odd that Clarisse's house was alive with laughter and conversation.
"When they reached her house all its lights were blazing. "What's going on?" Montag had rarely seen that many house lights. "Oh, just my mother and father and uncle sitting around, talking. It's like being a pedestrian, only rarer. My uncle was arrested another time-did I tell you?-for being a pedestrian. Oh, we're most peculiar." "But what do you talk about?"
In the society in Fahrenheit 451, it is common for people to avoid emotional connections and intellectual conversations. Since books are considered illegal and the word "intellectual" became known as a curse word, the people in the novel's society engulf themselves in the parlor walls that display bright colored and fast moving objects with loud sounds. The parlor walls, along with the "seashell" earbuds and fast driving, allow for people to completely avoid personal connections.
Take Montag's relationship with his wife for example. After returning home from work, he describes his room "like coming into the cold marbled room of a mausoleum after the moon has set. Complete darkness, not a hint of the silver world outside, the windows tightly shut, the chamber a tomb world where no sound from the great city could penetrate." He and his wife, Mildred, sleep in separate beds in a very dark and desolate room, while Mildred tunes Montag out by listening to talk shows on her "seashell" earbuds.
When Montag first encounters Clarisse's house, seeing people awake late at night with all the lights on, having intellectual conversations, and laughing, Montag begins to understand that Clarisse and her family are an odd bunch.

During their first meeting, Montag walks Clarisse home. When they arrive at the house, he is confused to see all of the lights "blazing." This is shown clearly in the text:

"What's going on?" Montag had rarely seen that many house lights.

Clarisse's house is so brightly lit up because her family is sitting around on the porch, talking to one another. Montag finds this odd because it is not a usual way of spending time. Look, for instance, at his relationship with Mildred. She spends all of her time watching the parlor walls, rarely interacting with Montag. The idea that they might sit out on the porch and talk for a while is completely alien to him.
In fact, the majority of the people in Montag's society do not live like Clarisse. They are encouraged to spend their time pursuing entertainment, like driving fast, watching the parlor walls, and going to Fun Parks, not sitting out on the porch and talking late at night.
Clarisse and her family are, therefore, depicted as outsiders because they do not conform to the same social expectations as everybody else.