Choices can destroy a concept, easily, and changing a decision like a disco ball vampire could be the easiest form of improvement. However, that doesn’t mean it is the best form. People lean on criticizing choices and risks over subtler and maybe more influential details.
To give a less controversial example than Twilight, let’s talk cursing. Swearing is the immaculate version of a preference that zaps all attention to it.
When reading the play God of Carnage for the theatre I worked at, I found the (irrationally popular) play boring and painful. There were many things to be said as to why, such as its predictability, its point being to hide the conflict for the first half, and its unlikeable and stereotypical characters, but I found one very interesting thing when the members of the board had to talk about it. They only gave a fuck about the “fucks” given. Twenty minutes of people complaining about the language and nothing else. The play was rejected for the season and that was the end of it.
Can swearing hurt a book? Absolutely. But it is still a matter of taste. It will hurt a story in that people will not like the choice being made, not because of the negative consequences swearing has.
Mistakes are things like typos, breaking continuity, sounding like it’s being made up on the spot, and essentially anything that directly leads to an undesired response from the audience, of which there are five: boredom, confusion, wasted time, insult from pretension, and expulsion from immersion.
Some of these are more subjective than the others. An author will never want the audience to be bored, but every once in a while confusion can be fun.
What does swearing do for the audience? It makes them mad that the author chose to swear. What does sparkling vampires do for the audience? It makes them mad that the author chose to make the vampires sparkle. Neither are dull (unless we were to go on and on about it), neither ruin the clarity of what is happen (except as to the reason why), these tiny details don't distract from the point of the story, and it's not like the audience is complaining about being condescended to. It could be that it's just unconvincing and jarring enough to remind you that someone is choosing these things, ruining the consistency of the world, but really, if you're so far into the book and you find that hard to believe with no qualms for anything else, you're not going to care.
Like most things in writing, there is no obvious line between the two. Sometimes a choice is also a mistake, e.g. infusing the token female into a script may led the audience to be expelled from the story, thinking only about why the author chose to make the character a girl. Often, what makes the book unique from others of its kind may not be benefiting the audience’s reception. Thus it becomes harder to decipher the difference.
Why would we bother though? What is important about identifying a choice or a mistake? Nothing much in the writing process, but when it comes to editing, it can solve a lot of internal dilemmas.
What is the difference between being yourself and brashly being stubborn? What is the difference between selling out and playing the game? What is the difference between keeping your voice and being arrogant?
Recognizing that people will often comment on the obvious before the important is a clear indication of what direction we need to take, if the advice is unusable, if it just needs to be dissected before it can be implemented. It says that "if I am offended by this, then I don't have to use it for it to be usable" and that pushing further into the conversation will bring out more important options from the reluctant critic.
Let’s take a more convoluted example into consideration. A story has a lot of characters. That in itself is a stylistic choice that has no direct consequence or reward without context. When receiving feedback, the author hears, “You have too many characters.”
Now, as a choice, it means that it’s a matter of tastes, which indicates that she will receive the opposite response from a secondary critic. This flaw in one man’s eyes may be the virtue for someone else. So it isn’t a “problem” per se, but it certainly doesn’t mean there isn’t one. A mistake needs to be changed, a choice doesn’t. In this case, as the number of characters is a choice, finding out the problem (“I was confused by all the characters” or “I was bored because of all the different back stories”) will allow for the author to take that specific suggestion or solve the problem in another manner. It may not be optimum to remove cursing from the novel on the grounds that having a bunch of people in prison speaking like they’re in a book club won’t particularly benefit the atmosphere, but, it might behoove the author to have a character who doesn't swear and gives legitimate arguments why others shouldn't. It also, of course, might be a hopeless cause that the writer realizes he's not going to win.
Actually utilizing feedback is not as easy as the outsider tends to believe. It is not just about eschewing egos or emotionlessly analyzing the advice. Quality is subjective; it constantly changes, not just by each different viewer, but by their moods, their ages, their cultures, their perceptions, and by comparisons. Not only does accurate editing require a great understanding of self, but of others, and often, feedback is not cut and dry. If my fellow writers in my peer groups and classes were to take every piece of advice they got, they would create the most homogenized work this side of binary. But if they were to ignore it, there would be no reason to be there at all.