We use a slightly different implementation for speed. You will notice some of the other forums are choking and slowing under load now. Some of the code they use was not built for very large forums that are as active as we are and thus don't need to be as conscious of speed. The ones that are busy tend to slow during active periods from inefficiencies. This software was designed to avoid slowdowns and implements a few things slightly different.

ANSWER: What we have to accomplish your request (this is a new feature) is at the top right of the forums you will see the word FILTER. Next to it colored in gold you will see the words on a dropdown select that says "Show all messages". If you select from the dropdown menu "Show threads I contributed to" that will show you all threads that you posted in.