about a. Yeah but the problem is that it isn't the character the writers are lecturing, I'm not sure if you ever cared to read through some of the stuff (a lot of it got deleted though because it escalated) that went on over on the Fenoxo forums. Also you misunderstood my point (which might be a result of how I expressed myself though), it's not about not allowing the player to pick how they want their character to act, it's about the lack of a choice in that. With some characters, all written by the same persons. Other characters are written with the mindset of the whole thing being a game that should center around providing an enjoyable experience to the players, not a tool for some writers to try and impose their set of beliefs about how relationships should be handled upon the players. Especially since the usual case is that there isn't even an option to play monogamous, the writers just assume every player is trying a harem playthrough and act antagonistic, which is really crappy towards people even trying to roleplay the way you describe.
about b. I agree, but that isn't achieved by getting into an indirect confrontation with the player, that's just petty and unprofessional. As I've wrote before, don't use your favorite (maybe even self-insert) OC characters in a porn game which is entirely centered around the porn if you aren't fine with them being treated as nothing but a help for others to jerk off to the sex scenes with them. I'm not saying the story parts and the interactions are bad, by any means, but things start to sour as soon as the respective writers start to take themselves, their characters and the fetishized interactions with them too seriously.
c. Yeah, but treating cliché characters in a porn game without any meaningful story like anything else than a tool to make the players happy just isn't a thing. That doesn't improve on the writing, it simply is a fools errand. I agree with what you say but it doesn't apply here.
For that to be valid there would have to be an entirely different level of intricacy and amount of interaction between the characters and the protagonist. As long as the majority of their scenes doesn't even take into account stuff like player virginities, body modifications, the adventures that happened and are happening & the characters aren't a constant presence throughout the entire journey, with meaningful impact on the events, they have no business being treated like secondary protagonists. So it is the other way around, first a character needs to act like a real person, then they can be treated as such by the setting their in.