To participate in a case discussion, you need to registered and logged in.
Underneath the case you will find the forum. There are two possibilities:
1) You want to write a new comment in the forum:
Click "Your opinion on this topic" at the very top of the discussion. After that you will find yourself in the mask in which you can enter a subject (which will be the headline of your posting) and the text. Your posting will appear at the bottom of the forum.
2) You want to write a comment to an already existing posting:
For this option, click on the symbol appearing next to the subject of the posting you want to write a comment on. Your posting will then appear as reply just under the original posting.