On the subject of cheating. To my mind in relationships the unofficial matters a great deal. Marriage is a legal contract and in a divorce things like evidence matter and should, but morally speaking it is not wrong to sleep with someone else when your spouse's actions have already broken the relationship beyond repair. At that point "cheating" is a mere technicality. In the courtroom those technicalities matter, but morality focuses on the spirit of the agreement not the letter. Most relationships in BADIK are of course not marriages, but if you think of them as verbal agreements the moral consideration is pretty much seamless. Breaking the agreement has no legal consequences, but morally the cheating is just as meaningful.
How does this apply to BADIK characters? Let's start with Bella. She has had no contact with her husband in three years and has reason to believe that he is dead. Her actions with the MC being adultery is a technicality. It's debatable if it should even be considered that since if James is alive he has effectively abandoned her. Bella herself feels guilty about it, because she has not fully moved on emotionally, but objectively there is nothing wrong with her actions. At least nothing wrong where James is concerned. Jill on the other hand has some cause to complain. As does anyone else who was led on by MC.
Jade on the other hand is definitely still married to Stephen. Those actions are adultery. It just so happens that Stephen's multiple adulteries across the years reduce Jade's to a legal technicality. Jade definitely isn't innocent in their marriage falling apart, but we don't at this point know how things were before Stephen strayed for the first time. Jade may have been an incredibly bad spouse in other ways. But even if she was, Stephen still let the marriage keep going. If he wanted to keep his morality intact, he should have divorced Jade much sooner. Likewise Jade should have started the divorce process herself. Rather than moving on she uses MC as a means for revenge. She is not good, just better than Stephen.
Sage is also technically in a relationship, if you play the fuck-buddy variant. If you friend-zone her until episode 7, it's not even technically cheating. But even with the fuck-buddy route she doesn't go beyond kissing MC without first getting proof of Chad's cheating. She should have broken up with Chad herself instead of trying to find out who his partner was, but even so all the blame falls onto Chad. The fact that the relationship was a lie to start with makes Sage's "cheating" even less meaningful.
Maya and Josy cheat on each other. Neither knows about the other so it can't be called revenge. They try to make their relationship work anyway, but they both did cheat. However, unlike Jade, Stephen and Chad, their actions are very limited and very much fuelled by circumstance. Neither of them makes it a habit and they regret the little that does happen. The wrongs are forgivable, but their innocence does get a stain. It's not just a mere technicality the way it is with Sage and Bella.
And now the couple who got us onto the subject (this time anyway). Tommy and Heather are in an open relationship. However they do agree on rules. The rules are different from the conventional "no sleeping with other people", but breaking them is still cheating. Heather only cheats on Halloween. She is drunk, very angry, regrets it immediately and later breaks up with Tommy. Not a habit. Tommy? Very much a habit. And he definitely understands that he is cheating open relationship or not. Otherwise he would just tell Heather instead of telling the DIKs not to tell Heather. He could try calling it asking for forgiveness instead of asking for permission, but he tries so hard to avoid letting Heather know at all that it's just straight up cheating. It is also clear that he is simply aware of Heather's temper and wants to avoid the consequences of her finding out. He has no remorse over the deeds themselves.
Lastly there is MC himself. Weirdly enough with him the argument is the other way around. He can fuck around a LOT and technically it isn't cheating. He doesn't even have the verbal agreement level of a relationship with anyone so what he does isn't cheating. Technically. Morally it's still pretty bad, but there are some considerations. He does try to have something more meaningful with at least the main girls, but they all push him to arm's length one way or another. Bella insists that she is a married woman and Sage says they're just fuck-buddies. They change their minds later and so it becomes a matter of when he did it. Threesome with Mona and Camila? That was Hell Week. It's okay. Threesome with Riona and Camila? Not okay. Jill on the other hand gives a lot of signs of wanting a long term relationship. The obstacle is even a consequence of MC's own actions. It's not okay to fuck others just because she isn't ready. Josy and Maya? Well Maya did say no strings attached and Josy didn't voice her disagreement, but is it really okay? Well he isn't actually cheating. Technically.
And on the subject of Tommy being an asshole. It's a matter of default behaviour. Derek is an asshole in Gender Studies, but that is not his default, so he is not an asshole. The "feminist" girls in that class however are definitely assholes. If you treat half the people of the world like shit just because they have penises, you're an asshole. Most of what Tommy does is pretty minor, but his default behaviour with strangers is to be an asshole. The people he is somewhat decent with are the exception, not the rule. He can be quite likeable when you get to know him and show him what lines he shouldn't cross, but he is still an asshole. He is way better than Dawe, but he is an asshole. And if you make certain choices the MC is being an asshole too. And you were an asshole for making him do that. And by "you" I mean "me" in some of my runs.