Are there any new grammar rules that are different then they were 40 years ago?
"The way people speak and write now is different from that of 25, 50 or 100 years ago.
It is I versus It is me or To whom were you talking? versus Who were you talking to?."
(G. David Morley: Syntax in Functional Grammar).
Should the subjective I fill the object slot in It is I?
Some people think It is I sounds a bit funny (especially young people), but it can be argued that it is in fact perfectly correct:
According to the traditional grammar being used here, "to be" is not
a transitive verb, but a *copulative* verb. When you say that A is
B, you don't imply that A, by being B, is doing something to B.
(After all, B is also doing it to A.) Other verbs considered
copulative are "to become", "to remain", "to seem", and "to look".
The rule for what he and others consider technically right is*not* (as is commonly misstated) that the nominative should *always*be used after "to be". Rather, it is that "to be" should link two noun phrases of the same case, whether this be nominative or accusative.
AUE: FAQ excerpt: "It's me" vs "It is I"