In one of my requirement I had two registration for two users. User had two roles. We have to build seperate form for two user registration.
By registrating from the specific url user will automatically get the respective role.
Now to give the seperate registration link for user we have to alter registration form using hook_form_alter() function.
Here is the code snippet how to achieve it.
In any case if we want to add some more links to user
In Drupal 7 you might have observed that when you enable the comments on any node at that time it also allows you to add the comments.
In each comment there is link to add the replay, but drupal doesn't provide any management to limit the depth/number of replay using interface or any module.
But we can customize using hook_preprocess_HOOK().
For comment display we have to create hook like themename_preprocess_comment() function in template.php file of theme.
After that we have to find the depth of the comment tree. You can find it using $variables['elements']['#comment']->depth variable.