"What a fool you are!"

Translation: Kia stultulo vi estas!

[brione]

Shouldn't it be "Kiel stultulo vi estas!" - "How like a fool you are!"

It seem that "Kia stultulo vi estas!" is "what kind of fool you are!"

[PatrickOsa]

"Kia" can literally mean both "what a..." and "what kind of..". In this case it's the former. Using "kiel" isn't as accurate, as it would denote how a person acts (in what manner), rather that the quality of the person