Sometimes spam occurs on this forum, or at least what appears to me as spam. This is a way to block it so you won't see posts by that user anymore. You will still see a notice in place of the blocked post that the post has been blocked. The same procedure as below can be used to reverse the block if you wish.
Log in to the forum. Go to Settings. Find the window "My Settings," then "My Account," then "Edit Ignore List." Add the name to the list and save it.