This is a spin-off of this suggestion: http://xenforo.com/community/threads/notices-post-in-x-forum.21083/
Here are two examples of what I mean:
1. I have an introduction thread. I want a member's first post to be in the introduction thread.
After they post, the notice goes away.
2. After a member posts in the introduction thread, another notice appears (because I selected the thread id requirement) saying Thank you for introducing yourself, enjoy the site, check out these threads too etc but that appears only because I selected the user has 1 post option along with the thread id requirement.