You dont get the point. What i'm trying to say, this still isn't the solution to prevent spam, it just makes people post more in a thread and when there's a new person they'd flood the page with welcome to the user. So I suggest self-introduction threads instead of one thread theory.
It's actually the same y'know there would be the same quantity of posts. And that's why there's the Welcome Gate and not the Welcome Thread. It's really designed for the newcomers, and besides... the page would lag more if it were to be flooded with the multiple posts of the people