FYI, your post title should use “whoever”, not “whomever”.
A good trick to tell whether to use “who” or “whom” is to replace “whom” with “him” or “who” with “he”. It’ll be immediately obvious (to a native English speaker) which is correct.
Whomever invented LED bus advertisements becomes Him invented LED bus advertisements
Vs
Whoever invented some stupid shit becomes He invented some stupid shit
Yes, that’s normally a good rule to follow, since “whom” is for a sentence’s object, but this is a special case. The clause in question is either a salutation that has no subject or object, and so either “whoever” or “whomever” is correct, or it’s a subject clause (a noun phrase, really) with an unnecessary, stylized “to” for the sake of comedic impact, in which case “whoever” would be correct.
FYI, your post title should use “whoever”, not “whomever”.
A good trick to tell whether to use “who” or “whom” is to replace “whom” with “him” or “who” with “he”. It’ll be immediately obvious (to a native English speaker) which is correct.
Whomever invented LED bus advertisements becomes Him invented LED bus advertisements
Vs
Whoever invented some stupid shit becomes He invented some stupid shit
It says “to”. To whom.
Yes, that’s normally a good rule to follow, since “whom” is for a sentence’s object, but this is a special case. The clause in question is either a salutation that has no subject or object, and so either “whoever” or “whomever” is correct, or it’s a subject clause (a noun phrase, really) with an unnecessary, stylized “to” for the sake of comedic impact, in which case “whoever” would be correct.
Clearly someone needed a technical education as a child.