One of the things that I always used to freak out about when teaching was seeing someone's knee go past their heel during Warrior 2, because I was initially taught that it could be dangerous for the knee. And I've heard that sentiment repeated in other yoga classes by countless other yoga teachers. But is it really unsafe? If so, then why do we allow the knee to travel forward of the heel in Malasana? When preparing to kick up into handstand? For that matter, what about when we climb up or down stairs, or squat in front of the refrigerator? What's the deal with the knee and the heel?
Are you practicing Virabhadrasana 2 with your hips "square to the side" and your front hip bone lifted in an effort to "make your pelvis more level"? These two cues seem to be very popular in Warrior 2, and while they might have some benefit early on, as your flexibility increases there is a good chance that they will lead to bony compression in your hip joints, which over time might wear down the cartilage and other soft tissues in and around the hip. This isn't going to benefit you in any way, and could potentially lead to osteoarthritis later in life, so it's good to learn how to recognize compression when it's happening so that you can back off. And if you're teaching asana, it's good to know how to cue the posture to help your students avoid compression.