Okay, I have found two other places this question, in feature-request form, has been marked status-bydesign (here and here). But I ask this as a discussion question because there is no explanation why the other two are by design.
So. Why is it the case that the accepted answer is sorted to the top even when I explicitly choose to sort answers by "activity" or "newest"? It makes sense for default view (sorted by votes)--an accepted answer is kind of a super vote, and you want users who come to the site via Google to easily find the best answer. But what's the use case for the user who has said "I want to see the newest answers" still seeing the accepted answer first, even if it's older?
I can think of one, but I think it's weak: the new user has clicked [newest] or [activity] while viewing a question, and didn't realize that the setting is sticky. So now he browses other questions and doesn't see the best answers at the top and so he decides SO isn't as awesome as it used to be and he leaves. Of course, this sets him behind his coworkers who do use SO, and his boss eventually fires him for not being a good programmer and then his girlfriend dumps him because she only dates programmers and he becomes a clinically depressed alcoholic homeless beggar. All because Kip thought that the accepted answer shouldn't be sorted to the top when the user picked a sort order other than [votes]
Is there some other usage argument for this, or is it just a limitation because of how the code is written?