How to choose the pronoun after linking verbs?
We must put the same word after the linking verb that we would put before the linking verb, mustn't we?
Do you know who was the man under the mask? that man was I.
But not one of them knew or guessed that if there was a man on this earth who knew better than everyone else that I was ridiculous, then that man was I, and that what I found all the more annoying was that they didn't know ... The Gambler and Other Stories
But I found a lot of examples where people had used it as following:
There was no way to prove — actually prove, really prove — that that man was me. The Illustrated Man
So, what are the rules and exceptions?