But do they do that because they don't know how to add to an existing thread?
For anyone who doesn't know, all you do is:
1. Open the thread by clicking on the thread title - under the column titled
Topic [b/]
2. Go to the last post on the thread - use the page numbers or Next [b/] at the foot of the page to scroll forward to the last page and last post.
Click on Add Reply which you will find below the last post on the right-hand side.