My observation of Danny is stark different. It became plenty clear from the get go that while Danny and Lisa shared a very exclusive and loving relationship, every now and then he would exhibit signs that he was having a very conflicted time whenever he saw Lisa with another guy. Normally, one would fly into a defensive rage and become protective about their girlfriend in such a scenario. But the Danny I came across never behaved liked that.
While not an outright beta and clearly willing to take a stand, he struggled to express his displeasure clear. Like he was fighting to get the right words out but at the same time failing to find those words, which would ultimately result in him and Lisa having an awkward moment and Danny breaking off the conversation. But then Lisa confided in her Aunt about it and she gave her the first clue. That he might be like Lisa's uncle, a guy who is into Netorase/Sharing.
And then came the second confirmation in the car ride home when Danny got mad at Lisa, even though he was the one who pushed her onto Calvin in a drunken stupor. I remember Lisa straight up didn't pull any punches and dropped the bomb on him about his cuckoldry like tendencies. While Danny was livid about Lisa fucking another guy, he became dumbfounded and couldn't utter anything back when he got told that even Lisa's Aunt believed he had such kinks. Like he already knew, but didn't want to accept it.
All in all, I know a lot of folks dislike Danny, and it's cool. PG has tailored the game in such a way that the player will ultimately decide what kind of person Lisa will be by the end of it, including who she ends up with, if not Danny. I however, actually like the idiot, and I've this feeling that his relationship with Lisa isn't meant to be exclusive. Like PG is sending a message hidden between the lines, that their love would actually blossom best in an open relationship.