How to approach HSF's question What skills, qualities and attributes would you bring to the role? without regurgitating your answer to their other question about what attracts you to HSF/the work experience section
I think the way you should interpret this is a 'Why you?' question. Essentially, what you want to do is to discuss your experiences and achievements, the skills/attributes that these experiences demonstrate, and how these skills/attributes are relevant for the work of a trainee. You do not have to discuss any firm-specific motivations or motivations for commercial law in this section.
As such, the only danger of repetition comes from discussing the same experiences/achievements here as you did for the other two questions. To avoid that, I'd try to be tactical with the experiences/achievements I mention in each section. Firstly, I'd avoid discussing more than two or three experiences/achievements in any of them. Secondly, I'd chose for each section the experiences that bring most value to it. For instance, if you have an experience/achievement that could be mentioned both in the 'Why the firm' and in the 'Why you' answers, and you have many other experiences you could use in the 'Why you' section but few other experiences you can use in 'Why the firm' section, you should include it in the latter.
Finally, my specific advice in approaching this section is to write two or three paragraphs using the following structure:
- Start by describing your experience/achievement in detail, using a STAR structure. If possible, quantify any results or impacts.
- Explain why your experience/achievement and its result demonstrates Y skill you have.
- Explain how Y skill is relevant for a trainee's success.