The guidelines for good answers (or its experimental variant formatting of much the same content) should probably include some guidance on the use of line rules.
I think they would best be used for separating less critical content when using a header would provide excessive emphasis. However, it could be argued that line rules could be used for separating sections of a text when a header would be excessively disruptive or when only one header would be required in the post.
What advice should be given concerning the use of line rules in answers (and perhaps in questions)?