Should we have who or whom here?
He's talking about people who run fast. I run fast. I'm who(m) he's talking about.
I understand that "who(m) he's talking about" is a free relative clause and we'd say "I'm the person whom he's talking about" (so I'd guess "whom"). Wikipedia says "Modern guides to English usage say that the relative pronoun should take the case appropriate to the relative clause, not the function performed by that clause within an external clause." I just wanted to double check that that still applies with "to be" and a free relative clause.