Personally I don't feel like I could make a post in the serious thread that couldn't be read as sarcastic or otherwise actually joking, no matter how much I meant what I was saying. If I started out explaining that, no really, I was very serious, that would just seem like set-up. It's like when Michael Richards went on Letterman with Seinfeld to apologize about using hate speech on a bad night for his stand-up act, and the audience kept laughing. Look at Kramer! Apologizing!
In my experience, no-joking threads are a bad sign at forums. Just have ignore lists and then people can block hilarious people if they feel the need. Or I mean, it is not hard to just skip over one-liners; are you wearing your fingers out on the scroll wheel?
I do like threads for replying to threads that you can't reply in though. Or ones you can, that's good to. Why I didn't make a new thread for replying to this thread is a mystery.