During one of my project work there was requriement to display the comment form on the non-node page.
Here in this context non-node page means the page other than node/nid.
I was using plain drupal without panels and other module. If we are using panels then we can always put comment pane in the related page.
As I was using plain Drupal i wanted to render the form via template file aka tpl file.
We can't directly do on node tpl file becasue in tpl file $comment is not bound to nid.
So i followed the approch to create the variable that stores the form and render in the tpl file..