comment-template.php

Good afternoon!
I can not understand algorithm of reception of comments.
From a theme file there is a reference to function wp_list_comments () which is in a file comment-teplate.php. The further work occurs in a file comments-template.php. But there is no cycle.
Where cycles for a conclusion of all comments are located?
I will explain that I wish to make: it is necessary for me, that in last comment to record the certain line was automatically added. I think, last comment can be calculated on id, or by date, remembering it in an operation cycle of comments and comparing to the subsequent.