In the kissing episode, my arms worked pretty well for putting a stop to it. He stopped moving when a wall got in the way. And when I (and the lady next to me, who heard the kiss sound and saw the push) yelled at him, a handful of people took notice and tried to get him to leave. They didn't notice that he finally chose to leave when I did...and followed me, but I saw and headed toward where other people were.
Oh, and no, I wasn't the first person he'd gone after that day. The other had an experience much closer to Noirin's (except in this case, he tried to put her hands on his crotch).