Is misplaced emphasis a form of mispronunciation?

If the question is "does stress crucially affect meaning in English?" then the answer is yes.

In a sentence, putting stress on various words affects the meaning:

• I don't love YOU. (rather, I love someone else)
• I don't LOVE you. (rather, I simply like you)

In each English word, the stress is lexicalized. Some words have syllable-final stress:

around, sustain, degree, parade, withhold

Some words have penultimate stress:

better, fashion, payment, differ

Some have antepenultimate stress:

Macintosh

And so on:

legislature

Many words are crucially distinguished by the stress, such as these noun and verb forms of words:

• You record a song and play it on a record.
• You insert an insert into a book.
• When numbers increase, you see an increase.

Also, more closely related to your example, we normally have different stress patterns in how we pronounce set phrases vs. ad-hoc adjective-noun combinations.

For example, if I say "blackboard", I place primary stress on the first syllable ("black"). This will evoke the image of a slate on the wall that you write on with chalk. But if I am actually talking about a board (say, made of wood) that has been painted black, I would call it a "black board", placing primary stress on "board". Likewise, the word "South Park", as a set phrase, is generally stressed on the first syllable.

Not all common phrases take on this stress pattern, and not every one of these types of phrases have taken on the same status for everyone.

You will find that most speakers will conform to these rules almost all the time, although a word or phrase here and there might be treated differently by a given speaker or dialect region. For example, around here I hear people say the noun permit with stress on the secondary syllable — I only use that stress for the verb form.

So, these are the facts. Whether or not any deviation is considered a mispronunciation is, as you say, subjective.

Consider the word Catholic, for example. If you put the stress on the second syllable (as it is in Catholicism), I think you will find very few people happy with your pronunciation.

So, yes — misplaced emphasis or stress can lead to significant mispronunciation.

On the other hand we have words like controversy, where the stress may come on either the first or the second syllable. An anal few like to argue for one or other pronunciation of that one — but most of us accept them both, and some even say both without particularly noticing.

So, no — not always.

Well, as the saying goes, you put the acCENT on the wrong sylLABle. That is a form of mispronunciation, but if everyone is "mispronouncing" something, then it's not really a mispronunciation. And if half of the people pronounce it one way and the other half pronounce it another way, then it's just a variant.

But, yeah, if your friend pronounces the show "South PARK" then he should be flogged. Or at least ridiculed. Or maybe just ... tolerated. Some people honestly don't hear the difference in pronunciations. The heavy Brooklyn accent, which swaps bird for "boid" but pronounces toilet as "terlet", gave rise to this misunderstanding I read about some years ago.

A teacher from the Midwest got a job teaching at an elementary school in Brooklyn. She took the children on a field trip to the zoo, where they viewed, among other animals, a bald eagle.

"Do you know what that is?" the teacher asked her students.

One little boy spoke up. "Sure, Mrs. Eisner. It's a boid."

"Not quite," the teacher said, determined to teach good pronuncation. "Tommy, that's a bird."

"Oh," the child replied. "I tought it was a boid."

That's not really about emphasis, but it illustrates the point that different people pronounce words differently. Also different groups. The British say BERnard while Americans say BerNARD. Neither is wrong, it's merely a difference among groups. Except for the Indian guy I work with who says "Oh no, I do NOT like vegeTABLES." He's just wrong. I don't care if a billion people pronounce it like that, it's still wrong. (And in case you haven't sussed it out yet, I'm kidding.)

I suspect it's an artefact of treating the title as a single word. In English, most words of two syllables have the emphasis on the first syllable.