I think the forum does it to prevent messages like this:

HEY GUYS I AM LOKING FOR A NEW FIXIE BIKE AND I WANT TO SPEND LESS THAN $100 WHAT SHOULD I BUY? I DONT WANT ANY BRAKES BECAUSE THOSE ARE FOR PEOPLE WHO DONT KNOW HOW TO RIDE A REAL BIKE. AND I REALLY LIKE ORANGE SO TAHT WOULD BE GOOD TOO.



Everyone knows that caps it used for emphasis when you really want to get your point across.