comment_forms in core/modules/comment/comment.module

Implements hook_forms().

comment_node_page_additions in core/modules/comment/comment.module

Builds the comment-related elements for node detail pages.

comment_preprocess_node in core/modules/comment/comment.module

Prepares variables for comment.tpl.php

comment_reply in core/modules/comment/comment.pages.inc

Form constructor for the comment reply form.

node.tpl.php in core/themes/bartik/templates/node.tpl.php

Bartik's theme implementation to display a node.

node.tpl.php in core/modules/node/templates/node.tpl.php

Default theme implementation to display a node.