Helluva Trio pg 76 ink (commentary) (Patreon)

Finally, all that obvious set-up gets to pay off when Moxxie taps into Loona's kink.

When I was scripting, I was really trying to figure out what Moxxie's and Millie's strengths were and how they would play out differently. Millie is more emotionally in-tuned with others and is more willing to confront an issue when she sees someone is bothered, but tends to get lost in the fun. Moxxie isn't as emotionally intelligent, but he is observant, and his high empathy can help him put the clues together.

So, I reasoned that Millie can recognize when Loona is struggling, like at the beginning of the comic, but Moxxie can recognize how someone "functions," much like he works with all his guns.