To give another deviant a direct link to this FAQ answer, use the following code in your comment or forum post:
How can I send a note to another deviant?
You can send a note to other deviants by the following methods:
1.) Visit the profile of the deviant you wish to note. Once on their profile you will see a button located on the upper right hand side entitled "Send a Note". Simply click on this and a small note window will automatically display.
2.) The second method is to visit the "Notes" section of your "Message Centre", by clicking on your messages link followed by the "Notes" tab.
Please be advised in order to use the notes system you must own and be logged into a deviantART account.