It's not grammatically incorrect anymore. It's a question of formality. Ending with a prEposition is considered informal. But your last example is incorrect. It's unacceptable to string two prepositions in a row. "Going with to" is bad grammar. It would be better to end that sentence with a preposition "Whom are you going to the party with," is actually correct. It's a predicate that can be connected to an object with "with" an object. "Going to the party with whom" whom is the indirect object
Growing up, going to school in the '80s, we were taught that it wasn't permissible to end a sentence with a preposition, even though every teacher spoke with the dangling preposition at the end. At some point the English language gave up that rule. People who are still saying it's not correct are unaware of that rule having been dropped.
"That is the sort of pedantry up with which I will not put!" - Winston Churchill.
I've heard that it has never been a real rule and was made up by someone and picked up and repeated by people who wanted to seem smart. I read about it in a book by Steven Pinker. Tried searching for it, found this:
The prohibition against clause-final prepositions is considered a superstition even by the language mavens, and it persists only among know-it-alls who have never opened a dictionary or style manual to check. [...] The pseudo-rule was invented by John Dryden based on a silly analogy with Latin (where the equivalent to a preposition is attached to the noun and cannot be separated from it) in an effort to show that Ben Jonson was an inferior poet. As the linguist Mark Liberman remarked, "It's a shame that Jonson had been dead for 35 years at the time, since he would otherwise have challenged Dryden to a duel, and saved subsequent generations a lot of grief."
I will correct my post a little because va-diim poses a good example of correct Grammer while trying to incorrectly correct me. va-diim goes on to say "going to the party with whom" which if turned into a question (simply adding the question mark) that also is a correct way to translate this exercise. You are going to the party with whom? It sounds choppy, it's not normal everyday English, but it is correct nonetheless. There is a reason, a good reason, why languages have grammar rules. It would be impossible to communicate without them. Punctuation rules and grammar rules can change the meaning of each sentence that is spoken. Let's eat Grandma Vs Let's eat, Grandma.
I think you are a little bit confused.
"Who(m) are you going to the party with?" - correct
"With who(m) are you going to the party?" - correct
"Going to the party with whom?" - wrong
As simple as that. The fact that you brought up an example of a grammatically wrong sentence (#3) does not suddenly make one of the correct examples wrong (so either #1 or #2). I don't see how example #3 influences the first two at all.
With questions, there's another structure to be aware of. While questions in English normally exhibit fronting of the question word, there are also "Wh-in-situ" questions where the question word occurs in the same place as the corresponding noun phrase in a corresponding declarative sentence. This is common in "echo questions" where a speaker indicates disbelief by repeating a declarative sentence with a word replaced with an interrogative pronoun, as in the following short dialogue:
"You're doing the project with Dan." "I'm doing the project with who?" In questions of this type, the pronoun who would be used in normal/colloquial speech as the object of with, and whom can be used as a more formal variant. Posted by the user sumelic Dec. 30, 2016