There are two parts to 3.5, which is why I bolded the second part.
There's a difference between pointing out to someone he's doing something wrong and why, which I do regularly in the hope it will save them a sanction later, than threatening with sanction.
Point things out nicely if you can, post a sanction if you must. Don't make threats about sanctions. At least, thats the way I understand things and the way I do them. Not that I've ever posted a sanction.
Edit: There's a difference between pointing out what someone is doing is sanctionable and threatening them with sanction.
