"Reply" button not show up

This is a weird problem:

Joomla 3.3.0 website, installed Komento v1.8.2, core article system (com_content).

Already set to allow Public to "add comment" and "reply comment".

But, the "reply " button did not show up on the frontend comments list. Though the Comment Form really shows.

Checked all those configurations of Komento, all seem OK.

Have no idea what is wrong, why the 'reply button" did not show up?

For example, on this page:

http://www.zooly.org/gift-box/591-zy1222

you can see the Add Comment form, but can not see the "reply" button which supposed to be at the bottom right of each comment item block.

Anyone can give me a clue to solve this? Thank you in advance.