To check the "quote message in reply" in quicky reply box, you have to multi-quote another user's post, which can be found next to the "quote" button/icon at the bottom of every post.
If you want to quote someone, just click the "quote" button/icon at the bottom of that particular post.
EDIT: I got it wrong apparently... I can't click "quote message in reply" even though I multi-quoted your post... : /, well I guess you shouldn't use quick reply when you wanna quote... I don't do that, haha