There was actualyl a good thrad like this on Fakku this morning:
http://www.fakku.net/viewtopic.php?t=18556&start=0
Where Aura and Blue123 offered to answer a lot of questions.
Most of us are too busy/afraid to post on the public side of the forums, but eventually they'll get used to it I think.
We do, however, read threads like the one you mentioned. They are good tools for us to see what we think worked and what didn't.
For the Act 1 that you are playing now, the majority of the writing was done by Aura and A22. However scenes that involved any particular character were initially written by their path writer, then edited by Aura to fit into his game flow (which no human can understand).
Past Act 1 we all work almost exculsively on our own characters, but we post each scene in the Dev Forums for comment and discuss them in the IRC channel.
Personally, I like Shizune, but I do think that she is a strong enough character to split the audience. "Weak" characters like Hanako will ususally be met with a mixture of reactions, but someone like Shizune will completely polarise the audience. And that's not a bad thing; in fact I think it means A22 is doing his job.
I think I was probably one of the reasons for pairing up the girls due to my original "Grid" design for the game flow. I can write essays on how much of a bad idea that is. But part of that involved putting the girls into logical pairs to make the grid work, and that stuck.
But even in the early days of the development the girls were paired, especially Hanako and Lilly. Their Mother-daugheter relationship is cannon from before any of us can remember.
Kenji is one of the many side characters that we used to populate the game, but A22 is the guy that turned him into the Picnic-loving man we know today.
Some devs are still in school/university, others work, others don't. But no-one works on the game full-time.