With what's already shown, even a completely innocent thing would look like she's doing another thing if we didn't know that she's just eating ice cream while Naoto holds it. Now imagine that scene with the viewpoint only showing Luna and not the ice cream, slap a door in there blocking the view, make her stand in a hallway or something. Seems familiar?
No? Then what if we didn't know that in the
bottom panel here, she's licking melted ice cream off Naoto's hand, what's the first thing to come to mind? How about
this page alone? If we didn't know that's melted ice cream, what else could that white substance be?
It's the same thing, but for those examples, we are given the answer.
The only pattern I'm seeing here is that the author is deliberately not showing what's actually happening, just to mess with the readers. I said it before and I'll say it again, Schrödinger's Slut, is Luna for the streets, or is she not? Naoto himself is leaning towards Luna's banging a guy every night, but is that truly the case? We'll never know which until the author shows us. Until then, whichever way one interprets it is on us, the readers.