1. Log in
  2. Click the down arrow next to your username in the upper right of your screen
  3. Click on "User Settings"
  4. Now click on "Account tab"
  5. Now scroll down while looking at the left of your screen until you see "Conversation Detail" Just below that is "Display Mode" select "Latest Activity"
  6. Save your changes at the bottom of the page.
Also this is where you can create or edit your signature.

This will set your account to display all this way. If you just want to make the change to a thread you are viewing then just above the left of that thread are two tabs. One says "Posts" and the other says "Latest Activity" just click your preference.

NOTE: It looks like if you choose to have the "Latest Activity" activated the posts will not show the members signature. It only shows when you select "Posts" Do not know why they made it this way.