This one isn't going to work like that, I'm afraid. It feels like it's not descriptive enough, yet I'm hesitant to work it out fully as that's going to be making existing points too long.
People won't see this as obvious (and those that do will hopefully already be aware and moderate their tone). Also, I'm a bit hesitant against putting something about 'tone of the answer' into a faq that's likely going to be used by people to moderate said answers too... If something isn't nice, we have the CoC for that already, and rude/abusive flags.