At the end of the day, it's fuzzy.
Audience reaction is an element of impact on audience, but it also includes the connection created by dancers via their nakhra. Does the nakhra create a sense of connection? This can be gauged by observing dancer nakhra and keeping an eye on the audience in terms of their body language and engagement. It's really just intangible stuff at the end of the day. Judge's with experience can pick up the "vibes." But, it's probably safe to keep all audience related matter out of the rubric.
But, what happens when VCU comes to a competition in California, has no fan support, and yet the audience LOVES their set and swag. Shouldn't VCU be rewarded for winning the audience over? Shouldn't their ability to connect with a room full of people who are there to support OTHER teams be recognized? What do you think arjun?