TO "WHOM" IT MAY CONCERN
Whenever caught in a "who/whom" bind--and this happens to even the most accomplished of the English language writers--here's a simple helpful trick to remember.
Think of the pronoun who/whom in other third person "he/him" or "she/her" terms. An example:
"He/she opened the door" as against the passive "The door was opened by him/her." Obviously, no one would say, "The door was opened by he/she." Right?
Same applies in case of phrases employing use of who/whom. These are often interrogatory.
Who opened the door? and its passive:
The door was opened by whom (and not who)?
(Recall the earlier "opened by him/her" example.)
"To 'whom' the word ... is pointed" should then be the right choice. No?