Inferred Survival: It's strongly hinted in Messenger that Leader is Jonas: the mentions of his blue eyes, his sister, and Fiona, the sled makes an appearance, and that he first discovered his powers via an apple.
Meaningful Name: Jonas is a variation of Jonah, as in the reluctant prophet Jonah. Jonas knows that what the community is doing is wrong, but he is afraid to do the right thing and leave until someone around him is in danger, at which point he assumes the mantle of prophet and leaves the community at great risk to his own life, giving Gabriel a chance to live and releasing the stored memories back to the community.
Mentors New Hope: The Receiver of Knowledge who mentors Jonas is revealed to have had another protege in the past, hinted to have been his own biological daughter (in their society, children are assigned to parents other than their birthmothers), who committed suicide out of despair brought on by the knowledge she received from her mentor, and was unpersoned by the Community.
What Is This Thing You Call Love?: When Jonas learns about love through memories received from the Giver and asks his parents if they love him, they admonish him for not using precise language and say that asking "Do you enjoy me?" or "Do you take pride in my accomplishments?" would have been better.
Driven to Suicide: She couldn't take the horrors of the memories she received and decided to kill herself. This prompted the community to add a new rule, in that future Receivers of Memory cannot ask to be released.