Other hacks to improve blogger comment system are highlight blog author comments and numbering blogger comments which can be quite useful for you to make blogger comment system more useful and beautiful.
Now lets continue to how adding reply button to each comment in blogger.
As you would have seen this reply button in picture above, which will make you more clear, or check the below live demo to check its working.
Let now continue to tutorial how to add this to blogger comment system.
Step 1 : Go To dashboard Click Design > Edit Html > Tick the 'Expand Widget templates' box.
Step 2 : Press Ctrl + F and search for below code <data:commentPostedByMsg/>
And place the below codes after it.
You must need to change the YOUR-BLOG-ID with your blog id.Now how to get your blog id.Just got to blogger Design > Page Elements.
Now see for adress bar in your browser.You will get link like this.
Just get the id number in pink border and replace in the above code.And you have done now and just save your template.Now you will be able to see the reply button in each blogger comments.
Now Some customization to reply button.
Some users will like to want to keep reply button instead of text [reply].So just replace [Reply] in red in above codes with below image link and you will get reply image instead of that text.
source : http://www.anshuldudeja.com/2010/07/how-add-reply-button-to-blogger.html