On Firefox 21 - Win7 when you hit "Reply" on a post to quote it there is no blank line between [/quote] and your reply. I think it will look better if the editor add a blank line between [/quote] and the line where you start typing your reply.
Regardless of the line or not, one will appear after you hit submit (in accordance to the HTML styling). I believe this was already reported and deemed Not a Bug. If anything, the way you phrased it, it seems more of a suggestion.