At the bottom there's a textbox where you can post a general response to the whole discussion.
If you hit the "Reply" button beneath someone's message, their whole post gets instantly dropped into the textbox as a quote, ready for your answer.
Pressing "Quote" instead stores that person's message in a quotes bank. Later, you can drop in every saved quote at once by hitting the "Insert quotes..." button that appears below your textbox. Extra perk: this lets you tuck away a reply from one thread and then quote it inside a different thread (I've never actually done it).
As you can guess, that gets unwieldy if you're answering every full post. A better approach is to select just the particular bits you want to address. Doing that makes a little "Quote | Reply" pop up, and only your highlighted text gets included.
Hopefully that made sense lol
