Once you choose a forum and open a thread notice the Display Mode selector in dark brown on the right of your screen, top of the thread. You have some distinct choices to make. You can view the all the messages linearly or in hybrid mode which gives a bit of each choice. The choice is entirely yours. Try clicking all three modes to find the method you like best.
To test make sure you are viewing a thread with 3 or more messages.
To test make sure you are viewing a thread with 3 or more messages.