Perplexing padding problem

I’m putting together a WP theme, and I’ve come across a problem which I can’t figure out for the life of me!

Here’s a screenshot:
https://www.codebotics.co.uk/files/screenshot1.png

As you can see, the author/gravatar section for the first comment doesn’t have left padding consistent with all the other comments, and I haven’t a clue why. The classes are the same for all comments, and Chrome shows that there isn’t any padding be added by anything to the first comment.

Does anyone have an clue why? I welcome any suggestions no matter how far fetched!

Thanks in advance!