how to enable comments on all posts for all users

where else i have to on this ? i think admin – settings – discussion is the only place where we have this comment settings

I looked again and found one thing,actually comments on category pages work ok i.e it shows comments form even if there r no comments already.
Problem which i mentioned above,i m facing that on my custom pages.Actually i have added a custom page and showed a category in that page like

$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$args= array(
	'category_name' => 'My category name',
	'paged' => $paged
);

and then used

www.mysite.com/?p=$post_id#comments

to show the comment link.When user click on this comment link,it shows the msg

“Sorry, no posts matched your criteria.”

But when i login with admin,the same page shows comment form.How can i show comment form for all users.What i feel is,the way i m doing,there are few global variables which r not set properly bt i dont knw the list of those globals and to what value shd i set these globals.
Here is the link of the site,search with location “Planes Dr Indianapolis”
and then click on “Review” link on the result locations.If for some reason above link doesn’t work,use direct link to comment page

http://www.veztekusa.com/booty/?p=149#comments