Rivalry often causes the response of bubblenesting too, as the male feels an instinctual need to claim territory. If a betta sees his reflection or another betta, he's more likely to bubblenest in response. (Another reason you may sometimes see bettas in pet shops nesting, due to seeing so many other males around them). You might try putting a mirror by Dapples and see what he does, he may start flaring and even bubblenesting too .

Here's Orion flaring at me when I was looking at his bubblenest