check my previous post elsewhere in this thread: if you reply to a specific post (reply link on the right-hand side), rather than to the thread (at the bottom of the page), your reply will appear underneath this post.
also note the difference in thickness between the lines between the different posts: thick line for a new post in the thread, thin line if the post is a reply to the post above.
i guess this behavious replaces quoting. it also works, i guess, but i agree that it’s confusing. and one might easily miss a new post if it’s not at the bottom of the page.