If I am not mistaken, this option would only be for blog comments. Even though I have misgivings about flag/report buttons, that strikes me as an odd choice. It feels like they are more needed in groups and chatrooms, maybe even profile comments. Is there really enough misbehaviour with blog comments to warrant this, or is it that blogmins don't patrol comments enough? You can make a minor case for everything on this site to add a report button, but that gets a little ridiculous.