Report Offensive Message

Number one is debatable. Often user click only reply; effectively cut out all other recipient that may need to see the message (and next messages, as result of this one).

I often had to tell user to hit the reply-to-all instead of reply button, just to make sure that everyone in that discussion is kept in the loop.

Actually this is why there is a button to reply-to-all. Otherwise, outlook will be a dumb tools.