Blogger's old commenting system was poor.The pop-up comment window was very irritating.Blogger 'not very recently' introduced the embedded comment form which is a much better way to comment.All you need to do is to go to your blog settings and under the comments tab look for 'Comment Form Placement'.Select 'Embedded below post'.That's it if you are using a blogger template.
If you are using a customised template like mine,there's an extra step.Just go to Layout->Edit HTML and check the 'Expand Widget Templates' box.Now look for this line-
<b:include data='post' name='comments' />
Immediately after this line,add the following line of code:
<b:include data='post' name='comment-form'/>
That's it.You now have an improved comment form.