I had a hard time too. I practiced. Now it is simple.
For me the reply button is useless. With the quote box you highlight only what you want to reply too, one quote at a time. Then when you want to respond, you go to the bottom and you will see a button that says something like include quotes. Then you will receive another prompt and you will see the comments within quotes. You can reply one after another.
It will be easier to for now just do one quote at a time. It will become natural.
COPA
