My old friend Jorge does that all the time
He finds where I am commenting, then purposely downvotes me to piss me off
Maybe that's the case...
Or it's just some bots downvoting you. There's a guy (who WAS) here named Systemguy and everytime every new post here gets downvoted we just know it's Systemguy. Most of the time it's just someone downvoting us all to piss us off or some suspended user here who hates us (COUGH COUGH fluffin COUGH COUGH)