The only way you can stop your idea from being used is to keep it a secret.
The unfortunate truth is that games, like most things, are 1% inspiration and 99% perspiration. The people who can build the idea are much more valuable than the person who comes up with ideas, so there's no value in the idea unless you can build it into a game yourself first.
If you're not capable of building it into a game by yourself, then there's not much point in keeping it secret, as it has no value. If you're in that situation you may as well think about how you can get some value out of it, such as using it to increase your reputation as a designer of innovating game mechanics, etc...
Regarding that article, I invented an original aiming control scheme for FPS games 10 years ago, which I still enjoy using more than the usual mouselook systems that haven't changed from Quake 1 to Call-of-Duty 9... and no one has ever copied it. Maybe I'm just biased and my system isn't actually that good, or perhaps gamers don't like change, or perhaps no game designer ever played my mod to steal it, but for whatever reason, I've never seen this original mechanic copied. So if, 10 years ago, I had simply blogged about my awesome FPS aiming, or I'd not published an implementation of it at all, the world would be pretty much the same place as it is now anyway, except that as is, I've got the experience of having shared my work
Maybe by discussing your idea before you release your game, you'll refine it into an even better idea
And hey, if EA comes out with "[First-Person RPG] 2013" in 6 months and has totally ripped off your idea, at least you can link to that discussion, and say "I was doing FPRPG controls like that before it was mainstream"
Maybe someone else already independently came up with the same idea, and are working on a game that uses it right now -- if you start the discussion about this idea now, then you get to claim that this other person just copied you, whereas if they release first, they'll accuse you of copying them!
Maybe the idea already exists in some obscure game from the 90's that no one played
If you want to make an idea public, but still restrict it from being used, you will need tens of thousands of dollars to draft the idea as a patent (via a reputable and experienced patent lawyer) and register it with all the world's patent offices. Even then, this doesn't stop other people from using the idea -- once they've used the idea, you then have to take them to court for patent infringement, at which point your patent will be tested (and possibly invalidated!), at a huge cost to you and/or the target. You'll also be labelled as a "patent troll" (someone who patents ideas, but doesn't build them, and then tries to profit from the work of others who do actually build things) and universally hated.
Also, it's fairly easy for someone to make some small modifications to your idea to work around the wording of a patent, so that they're not infringing (i.e. so that you lose your lawsuit against them).