As the title says.
WHO is a subject relative pronoun, and WHOM is an object relative pronoun.
I tried finding an answer to this on the site, but this sentence in particular is more challenging than something like "She's the woman whom I married." (I married her..."her" is the object of the sentence, so it's easy enough to say "Ah! This needs an object relative pronoun.")
I'm trying to reconfigure the sentence above in my mind to find the answer, but I'm having some issues. I feel the answer is "whom," but I'm not 100% on it at all.
"You're not the person who/whom I thought (that) you were" could be said as:
I thought (that) you were someone else.
I thought (that) you were a different type of person.
In these cases, even though the you is a subject pronoun (same as "he," "she," etc.), would it still count as being in the object position because "I thought about you (object pronoun) and thought you (subject pronoun) were a different person"?
There is the folksy (or perhaps a grammatically consistent and correct?) idea that if you can ask a question about a sentence and have the answer be an object pronoun (him, her, us, them, you as object), then you should use "whom." This also applies if you can recast the sentence to discover whether the noun in question can be replaced with a subject or object pronoun (as in the "She's the woman whom I married" = "I married her" example above).
But it doesn't seem to apply in this case. Or at least, I can't think of the question to reach the answer, or of a way which recontextualizes the original sentence so it's clear whether I should use "who" or "whom."
There is also the idea that if you can place a noun or pronoun after a verb, that noun or pronoun is an object and you should therefore use "whom" to refer back to it. ("She kicked him" = "He was the one whom she kicked.")
...unless the answer is actually "WHO"?
Thoughts? And yes, I realize that "who" is standard and accepted in the vast majority of English conversations, and that no one would bat an eyelash if someone used "who" in this case (or almost every case!), but I'm still curious about this one at a "technically correct" formal level, and not at a common usage level.
My apologies for the scattered thoughts.