The characters spoke in a very formal style. What effect did this have?
Think about the overall feeling of the society in the book. The way the characters speak is meant to add to that feeling.
In this book, the whole society has had emotion and love and things like that removed from it. We can see that, for example, in the episode where The Giver shows Jonas the memory of the family Christmas celebration. Afterwards, Jonas asks his parents if they love him and they can't even answer.
In our society, at least, formal speech is usually used in situations where there is not really any emotional connection between the speakers. We don't speak formally to our children or our friends. The formality of the characters' speech helps make the society feel more soulless and makes the characters all seem distant from one another.
Formality in speech is a sign f respect and despondence. The people in "The Giver" speak in a formal style to reflect the detachment of the society. The society does not allow for love, affection, or any type of emotion. In order for the speech to become less formal it would have to include emotions which have been removed from society.
The effect of the formal speech does not allow for fluctuations in mood or changes. It also allows people o all speak in a unified pattern. Since the government controls every aspect of the people’s lives it stands to reason that the formal speech patterns were also established by the government.