Reverse AIBUs annoy the hell out of me - yes I hide them, but not usually until I've got to the page where the 'big reveal happens'.
They are pointless. All you are getting is one persons idea of what the person they pretend to be is thinking and when you consider that most posters will twist details to suit their POV; that its unlikely that the OP is a mind reader and most people have the emotional intelligence of a cucumber, its bloody unlikely that we'll be getting the full story
There's terms for someone who goes onto internet forums and pretends to be someone else to back up their own story just from their own point of view, its called a sock puppet or a troll.