This week's giveaways are in the MongoDB and Jobs Discussion forums. We're giving away four copies of Mongo DB Applied Patterns and 4 resume reviews from Five Year Itch and have the authors/reps on-line! See this thread and this one for details.
When you make a post, there is a checkbox near the bottom that says "Disable BB code in this message." If it's checked, then those tags are disabled and won't render properly. In the thread you point to, all the posts with broken tags have that box checked. I don't know why, but for some reason, that's the case.