Pronouns

[Jonathon]

Put another way, a subject complement says something about the subject, while an object does not. In it is I/me, I/me says who it is. In I threw the ball, the ball doesn't say anything about I.

[rivka]

In sum, though some misinformed people may give you a bad time about it, it is perfectly okay to use it is me.

Or perfectly informed people who happen to be language snobs.

[Jonathon]

In other words, people who should know better.