Every strike is a damaging strike. Read the doctor report that SmackyBear posted.., i've had that kick landed numerous times one me cos I didn't see it coming and no real damage. We use it in Muay Thai, I never hear of serious injury because of it.
In the article Smacky posted it says that a kick to the side of the knee joint is more damaging, meaning a low round kick.. nobody is going to be taking them out of the rules now are they?
Yeah Ive used/had it used against me in Muay thai. It's never thrown as a kick to cause damage but is very effective at taking someones balance away and/or making them think about the possibility of that kick, whilst making it easier for you to throw something different.