Can't use Denormalization in comment blog

I try to create some comments for my blog. I try to use Denormalization.
After:
Router.configure({
layoutTemplate: ‘layout’,
loadingTemplate: ‘loading’,
notFoundTemplate: ‘notFound’,
waitOn: function() {
return [Meteor.subscribe(‘posts’), Meteor.subscribe(‘comments’)];
}
});
Everything it OK.
Then I change my code:

Router.configure({
layoutTemplate: ‘layout’,
loadingTemplate: ‘loading’,
notFoundTemplate: ‘notFound’,
waitOn: function() {
return Meteor.subscribe(‘posts’);
}
});

Router.route(’/posts/:_id’, {
name: ‘postPage’,
waitOn: function() {
return Meteor.subscribe(‘comments’, this.params._id);
},
data: function() { return Posts.findOne(this.params._id); }
});

But when I click comment button it can show detail comment and I cant write a new comment. Although I create comment_summit.html and comment_js.

Please help me to fix this error.

Thanks a lot,