I'd much prefer an interest in my comic than just saying "i liked ur thing, now like mine." It doesn't help me understand my audience if it's just done for a number. I usually go into regular promo once in a while and just post in a maximum of 3 the day of an update for myself.
I think your idea of the promo topic with the intention of garnering actual interest is good, but also borders on what is already there in the promo channel.
Then again... we do have lots of topics with people just talking about their stories. Imho, I don't like participating in those mostly because it detracts from a person going to my comic to find that info out for themselves. And a lot of fun questions for creators to share in the forums ask about stuff that some people can't take part in because of where their stories are, and how much they do/don't want to give away. Hmm...
But I think this idea has merit. Maybe it being specifically like a "library space" or "reading room" kind of thing. Like, "This is the reading room for the mystery genre for comics! And here are all the subgenres categorized under mystery with respective comics linked there!" or something! 