Otherwise, the only thing that comes to mind is StackOverflow functionality where OP can mark a single answer as "accepted" and push it to the top instantly (which obv. wouldn't translate well to general discussions).
the four disagreements apply to a comment section as well: the comment is factually wrong, the comment lacks information, the comment. draws a different conclusion from the same set of information, or the comment is philosophically opposed to my viewpoint. For an online comment system, spam is another category.