[Plugin: WordPress Thread Comment] problem with AJAX

Hi! I like this plugin, but i found a problem here.
I choose to use AJAX, but it doesn’t work.

On the description of this plugin, it’s said that:

If you wish to use AJAX, the comment objects of your theme must has an ID like “comment-xxx”. It’s a standard of WordPress themes now, yet some themes may still not meet this requirement.

So i think the problem’s come from my theme.
The questions are:

1) what is “ID like ‘comment-xxx'” ?
2) can i fix this problem? How?

Any help would be appreciated.