- The post doesn't have a tone that fits the HN ideal.
- The post says something that they disagree with.
This is a problem, because those two cases should not be treated the same. A post containing an unpopular opinion should not be considered equivalent to a post that is insulting or derogatory, for instance.
From a user interface perspective, the sensible approach would be to provide an outlet for the user to do express two things independently, rather than attempting to modify behaviour through appealing to their better nature.
A separate 'flag' option would make a lot of sense.