Username appears instead of display name

Good day.

I have just started a blog and while the posts appear with the correct “display name” as the author, my comments appear using my user name. This means that to have my display name I need to log out and enter the name I want displayed before entering the comment. People do not have to register to comment and the template is “Elegant Grunge” if that is helpful info. Is there some way to make it use my display name?

Thanks a lot.