If your site's like mine, people consistently use the Contact Us form to ask questions that are better suited for the forums. I searched all over and couldn't find a way to put a message explaining what to use the form for. So I made my own way.
This plugin lets you set a custom message to be displayed above the contact form, using a WYSIWYG editor.
Built on 4.3.1, and tested on 4.2.9 (and later 4.4.4). I make no promises this won't interfere with other 3rd party alterations to the Contact Us form.