Almost never. Only if it seriously offends me to my very core. I never report shade though, unless its extremely ruthless toward my own fave. I think I've reported 2 posts since I joined.
The people that do report just think it's a big game. I can understand threads getting out of hand and negative remarks being exchanged all over the place but it pissed me off when I see someone's opinion reported when it's clearly coming from someone who is a fan of that celebrity that they think was "shaded." Totally immature.