Here is proof.
GM is hiding this because they don't want thousands of people doing it. But in his post he even mentions "we are looking into reports of roll spoofing" and that's what this is.
This isn't client side, and it's the easiest thing in the world to do. As far as getting caught, when you are in a random PUG people aren't paying too much attention. They see a yellow text say roll and they believe it. Out of 100 people maybe one has a seperate chat box for system message and general, and out of them 10% would notice it, so its like 1 out of 1000 chance. But then you have 1000 sunmotes, each costing 1,000g. That's 1 million gold before you get caught, and if your smart that 1 million gold is shipped away to a safe place.
And even when one person out of 1000 finally sees you, so what? First he has to report it, and most are too lazy. Second blizzard has to investigate and decide what to do. There will be no evidence that you did it 1000 times, only once. So maybe you get a warning if they even report you.
See my screenshot. The guild master is telling he is going to kick me because I win all the sunmotes. lol. They know something is wrong but can't figure it out. But they only know because I did it a hundred times to the same people. If you do it in pugs, its always new noobs to exploit.