I've read in a book that I should "use the subjective case if the pronoun is the complement of the linking verb to be".
That is the following sentences are correct:
They believed that the thief was I. / Hey, it's I. / Yes, this is she. Who's calling?
OK, a rule is a rule. I don't mind using it, but I have a question for native speakers:
Is this way to say it heard in everyday speech? Will it sound deliberate/unnatural if I use it?