Lily would be called in for chastisement if she continued to call attention to individual differences.
Chastisement is another word for punishment or scolding. It is not clear exactly what being called in for chastisement means, but most likely a town elder would explain to Lily that she should not mention traits of individuals because the community considered it rude.
No one mentioned such things; it was not a rule, but was considered rude to call attention to things that were unsettling or different about individuals. (Ch. 3)
Lily has been rude because she mentioned Gabriel and Jonas’s “funny eyes.” Jonas and Gabe both have light eyes. It is uncommon for anyone in the community to have light eyes, and this is why Lily thinks they are funny looking. Jonas is upset by the comment because being different from the other citizens makes him uncomfortable.
The community prizes Sameness above all else. This means that everyone looks alike and acts alike, and differences are minimized. No one calls attention to them. No one values them. Being different is dangerous, because it might make people uncomfortable.
The community has strict rules for behavior, and they are strictly enforced. There are cameras everywhere, and every interaction is recorded. The community elders know what everyone is doing, and public commenting on individual infractions are common. Parents are also expected to teach their children proper behavior and control it, and this is why Jonas “waited for his father to chastise Lily.” Errors by children reflect on the parents.
But each such error reflected negatively on his parents' guidance and infringed on the community's sense of order and success. (Ch. 6)
Jonas is disquieted by the incident. He does not like being seen as different. Calling attention to Gabriel calls attention to him. In Jonas’s community, the only other people who have pale eyes are a younger girl named Katharine and The Giver. The comment about Jonas’s eyes foreshadows the importance of those eyes. They indicate that he has the Capacity to See Beyond, and that is the reason he is chosen as the Receiver of Memory.
Job assignments are the only time when differences are relevant. The community tries to identify each individual’s strength and give the person a job that utilizes it. After Jonas is selected, it becomes clear that pale eyes are the least of what makes him different. His community will rely on his differences to save them from the memories of their past.