To the right of the "reply with quote" button is a "Multi-quote this message" button. You have to click the multi-quote button in the original post(s) and then click the "reply with quote" in the newest post.
Both or all of the posts will be in the message window in their entirety , so you'll have to edit anything in the original posts you don't want in your message.
I'm feeling like a part of the community now