The issue is that for older posts, the user's usual choice won't necessarily make sense – if a post comes from the time before comment nesting, it seemed unlikely that a user's usual preferences for sorting would be the sorting they want, because the comments will be harder to read on anything other than "sort by oldest." (this is for posts earlier than around 2009)
Oh, I misread the first priority - I thought the author of a post could choose how readers would see the comments. (Which would be a reasonable opt-out feature.)
Comment Sorting
Comment Tooltips
AlignmentForum
Bug Fixes