I am writing this comment because I feel like you were downvoted without a specific explanation as to why, and your post was made in good faith. If I made a post like yours and got downvoted, I would hope someone would be willing to take a karma hit to explain to me their reasoning, so I will do the same.

First, I think your sentence is partially correct. I generally believe that ineffective writing will not polarize people, because ineffective writing does not motivate people to do anything or have any serious opinions on it. Someone who posts something emptyheaded and unuseful will generally get very few upvotes and not generate a large discussion thread. I think that better writing will challenge people's assumptions, or bring interesting topics forward, and then people will have opinions, and opinions are polarized.

However, "Good writing polarizes people" is probably being downvoted because the best writing, at least in the sense of "let's write a fanfic that makes people want to learn more about rationality", would not polarize people and get them to write negative reviews on fanfiction.net. The best writing would cause people to be all like "oh, this is an interesting topic, and this writing is enjoyable to read. Not only will I read more about this topic, I will also continue reading this fanfic." I think that the best writing would somehow convince people that hpmor was awesome, and that they should come to lesswrong, read all the sequences, and then write high-quality comments. So good writing polarizes people is misleading since the best writing converts them.

If your statement is that the best writing polarizes people, I think you can expect to be downvoted because many people think the best writing convinces people, rather than just motivating them to write angry reviews. If it's true that excellent writing convinces people and good writing only polarizes, and you're making a more nuanced point, like that there's an uncanny valley of writing effectivness, this still does not make your comment super helpful, because it seems to me that the next step is "well, how could this be better so instead of just polarizing people, it convinces them" or something.