You're sort of opening up a whole other (but also much more interesting) discussion here about what then constitutes "player interference"
As I said, Ian and Lena interfer extremely often with the other characters. This by design and part of the game.
So what happens if Ian and Lena wouldn't be there? E.g. Perry wouldn't get either Emma or Cherry because he shy by default and only Ian willing and able (skillwise) to help him would change his character.
Louise hooks up with Jeremy regardless of Lena. If Lena isn't around, Jeremy pushes her to meet Ivy and it leads to the blowjob and they break up. If Lena is there and decided to interfer in Louises business (which requires higher friendship points that aren't there by default), then Louise is quicker to question Jeremy and Ivy and they break off before they even went to Ivys apartment.
For example why did you pick for Lena to not tell Louise that her "boyfriend" is cheating on her? I'd argue that picking the less friendly option of keeping it secret for no reason is player interference rather than making the choice a real friend would make.
No. You can always hide it from her but you can't always tell her. Lena's friendship to Louise is optional (at least the extent of it). If she is a loose friend, then you don't interfer in her business.
I'd also argue that he gets Alison only if Ian deliberately makes the choices that disfavour him.
No. If he stays with Perry and Cherry to not be a dick to them, Alison already enjoys Jeremys affection. And getting it back requieres high charisma.
And imagine Ian isn't around: Alison would response to Jeremy. She is always interested in him, its just that a confident Ian who seeks her out on his volition is her Number 1 dream husband material, while Jeremy is just a fuckboy to relieve her of stress. This doesn't devalue Jeremy.
Can you explain why you see this as "interference"?
Because its not the default option. It requires higher friendship points with Louise. Not telling her is the standard "so nothing and let things play out and let them make their own decisions".
What happens off screen?her sucking his dick?
Is Louise there if it happens off-screen?
Yes, Louise comes home, tells Lena about it, cries and even makes a move on her if she has high friendship with her.
He doesn't score with Emma unless Ian gives his blessing to go after his sloppy seconds.
No, Ian doesn't allow Jeremy to do so. He merely informs him. Jeremy simply never considered Emma and Ians encouragement gave him he idea. Then he approached Emma and she agreed on it wholeheartily. This is much different than Ivy asking Ian and Lena. Emma (and Alison and Louise) find Jeremy attractive and valuable for a fuck.