Add a reply option to blogger comments like Wordpress

STEP #1
Log in to Blogger, go to Layout -> Edit HTML
and mark the tick box "Expand Widget Templates"

STEP #2
Now find (CTRL+F) this code in the template:

<b:include data='comment' name='commentDeleteIcon'/> </span>

Now copy one of the below codes and paste it just after the above line.

Code:<span><a expr:href='&quot;https://www.blogger.com/comment.g?blogID=YOUR BLOG ID HERE&amp;postID=&quot; + data:post.id + &quot;&amp;isPopup=true&amp;postBody=%40%3C%61%20%68%72%65%66%3D%22%23&quot; + data:comment.anchorName + &quot;%22%3E&quot; + data:comment.author + &quot;%3C%2F%61%3E#form&quot;' onclick='javascript:window.open(this.href, &quot;bloggerPopup&quot;, &quot;toolbar=0,location=0,statusbar=1,menubar=0,scrollbars=yes,width=450,height=450&quot;); return false;'><img alt='Reply To This Comment' src='YOUR REPLY BUTTON IMAGE URL HERE'/></a></span>

Now, in the above code replace the texts in BLUE with your "Blog ID" and the texts in RED with the "Reply Button Image Url".

Now click Save Template

Important ! 
In order to make this work you must add your blog Id .
What is your blog ID??
Simply go to your layout page, posting page or any of the pages and copy your I.D. from the address bar at the top of the page.

Replace URL of image with any image of your choice or you can choose one from below- 

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-p_FBiZjVAJmyxerHHJnWjGFilS15cuiYPv40mqV9epKnrTmvpZ7ljFccH_KrHcNDUHd9T5gg5rPE7B9VqE0_Z0YVB8SK9Le3YqqndlxDHatjXJvgu5wd6u0p09f3_5XZexiePDbfcssj/s320/reply01.png

 https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6np6b5qAKw_7tNnY6JQiZvxzDj3UNmSbsB_-w3N4jA58eelIXnMlR4UMe1rku3-oHFd2_nXCp2N39sYRKoGAuwOLkGNM3qMN-i6Rlo3Z0tLqQWP3r7OxNi02s7PKXtNEBaflh-EVpWQ_v/s320/reply03.png

 https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgU-HhbABqNJlMqE3xoW-m_hgMHD_1oLzEKsclbDUGIgLl10YW5Ci2D6LSuCSuwlsli0HppzD33N9d9UCPkJsBuqxRirPWAgLSflfJi9sl8HEOXE2yLwnb_TvseBQpurKVFM2jj0CfQRQP4/s320/reply04.png

 https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9DQyq65grFn8va6GsMx6174Qqs7XiOhA7W-_l6nM7MprRbPEPvRFmir2xeHo7M0n20r-1sMutsJQWhFqfftBwXdykJsE3d7pWZf21BzgvMbDBhJwtaXT2VMlMfFXvf4f9YsS8wKZjUdF4/s320/reply02.png

 https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgaLGzqR7bnCYcnEJWpZcwOICCrlGDg14Y1tKFYUOUOAWoN2LQN9ZuL4shdcIGHThvr6ApDZCWMe-G5jxbgBDmZcpAPCE8v2hQv323I1E6AIuaXicNozIDsBpCy5DsFJFmpLLC822qC5U9A/s320/reply05.png