Learn Italian: «Il corsivo è perfetto!», esclamò l'editore. - "The italics are perfect!" the publisher exclaimed.

This is called post-verbal subject inversion, which is highly common in written Italian when reporting direct speech. By placing the subject (l'editore) immediately after the reporting verb (esclamò), the sentence flows much more naturally in a narrative than it would using the standard English word order.

Does editore mean "editor"?

No, editore is a classic false friend! It actually means "publisher" or "publishing house". If you want to talk about an "editor" in Italian, you would use redattore (for newspapers or magazines) or curatore (for books).

Why is il corsivo è singular when the English translation says "The italics are"?

In Italian, the italic typeface is treated as a singular, uncountable concept: il corsivo. While English uses the plural form "italics", Italian uses the singular noun, so the verb and adjective must also agree in the singular (è perfetto).

Why use esclamò instead of the passato prossimo (ha esclamato)?

Esclamò is the passato remoto (historical past) tense. While you would use the passato prossimo in everyday conversation, written narratives (like novels and stories) use the passato remoto for completed past actions. Reporting verbs attached to direct speech in literature almost always appear in this tense.