I have a blog site in Sharepoint 2010, by default we have a option for comment on the blog, now I need to have reply to the comment posted on blog. Is there any out of box feature to to achieve this.
You'd have to create a custom site definition using the blog site as your starting point. https://msdn.microsoft.com/en-us/library/office/ms454677(v=office.14).aspx Then you'd have to override the Comments list functionality to add your own behavior. https://msdn.microsoft.com/en-us/library/office/ff728096(v=office.14).aspx