Reply, allows you to quote one person and will automatically insert the quote into the box you type in.
+Quote, will allow you to select multiple people to quote. Once you have everyone you want to quote, scroll down to the box you type in and right below the box it will say "insert quote". Click that, which will then bring up a pop up and show you the quotes you selected. Just click "quote these messages" to insert them all into the box that you type into