Thank you for your reply.
I installed firebug and went through all the styles in there, and found that it is mostly controlled by the css called 'style.css.'
However - it is impossible for me to locate the 'reply' comment box. Every change i make on the different comment box styles there is to be found in this huge document, will change all comment boxes globally.
I can see in the frontend, that there is SOME difference, since the reply will have a left margin of 20 px. But i have not bin able to locate that margin to only the 'reply.'
To explain myself better i have made a screenshot:

Can you please help me locate the 'reply' comment boxes and the editing possibilities for that and not the overall global comment boxes?