I added some quoting facility, not being sure of the better way to handle it.

I though about automatically adding the content of the last message on quoted style in the textarea. I dropped that idea since we may want to quote an older comment and since the textarea may seem small already.

I dropped the idea of using some kind of cheap javascript in order to provide something for every users.

So I ended up adding a button that show the comments in a quoted style easy to copy/paste. Why a button and not a configuration option? Because it's probably best that people get always the (more or less) unaltered content. But it's not a religion, user input could be interesting in this regard. And if people wants it to be an option, we'll make it a configuration option.