It's slang that started in...I believe...deleterius (I likely have the user name spelled wrong), or at least that's where I first saw it used excessively.

'Sporking' is essentually tearing into someone else's idea or character or way of playing on a rant board. it came about probably from people joking about getting 'sporks' (those spoon-fork combos some fast food chains provide) and going after a particularly offensive player and repeatedly stabbing them with said sporks.

BRPS is not nearly so harsh and cruel as Deleterius, but we've all seen some of the doozies there--hence, 'sporky boards'. Because a lot of the posts really do just tear into folks.