I see karma on posts fluctuating (in particular going down) more than I would expect coming from other vote-based websites. Is downvoting really used here for posts that are not spam or trolling? Or do people just change their minds a lot?
The FAQ has: We encourage people to vote such that upvote means “I want to see more of this” and downvote means “I want to see less of this.” But I guess I’m surprised if people actually behave that way? And that some posts are controversial enough to receive active downvotes vs passive ignoring.
Vote aggregation is how we get "this is worth being seen by people reading LW" from "I want to see this." Individuals know a bit more about their own personal preferences than they do about the personal preferences of others. Asking people to judge the personal preferences of others can only lead to a decline in accuracy of reporting.
I think the point is that what people on LW like should be worth reading. I can imagine a few different general situations and only in the most ridiculous situation does changing the voting basis from "what you want to see/don't want to see" to "what you think the community should read/should not read" improve the content.
Situation 1: LW users have good taste and want to see more worthy posts.
In this case the switch would at best cause no change and at worse decrease the quality of posts because users may be worse at judging the opinions of others than they are at judging their own opinions.
Situation 2: LW users are unable to judge a post's worthiness.
If the users aren't able to judge worthiness, voting on what they think is worthy can't actually improve their score.
Situation 3: LW users have bad taste and what they want to see has little/negative correlation with worthiness, but they can still judge worthiness well if asked.
In this case switching the voting system would be effective. But this sounds ridiculous on it's face! How could someone capable of judging worthiness not actually prefer worthy content to unworthy content?