Chuck said
I see that some people can quote two different posts in their new post.  How is this done?  

If you start a reply (either just by clicking “Add Reply” or “Quote”) you can scroll back up to another post and click “Quote” and it will add that quote block to your reply. You can then edit as you wish.

You can also click the quote marks in the edit tools of your reply and add whatever you want in the quote text, even if it isn’t really a quote (useful for making data or other important things stand out).

Steve said to Chuck:

Like this

Or you can get crazy and edit the html directly with the angle brackets button (“<>”).

Steve