I don't understand what you mean by 'reply' button... There's a 'comment' button that I'm using. Anyway, I didn't use it because I got two of them for my son's birthday :)
I see. Yes it makes a huge difference!! Did you know when you are responding to a comment if you slide your cursor across the bottom of the comment box you will see *reply* light up in blue and if you click on that to respond it sends an email to the person you are responding to? It is the only way someone knows you answered their question without checking back.