The same question could be asked of any WordPress archive page including these:
Home page when set to show archived posts
Categories
Tags
Dated archives
Search results
Anything that reuses content
The short answer is highly unlikely, on a post the comment text is loaded with a post and possibly dozens of other comments.
On an SEO blog comment URL the comment alone is loaded with the option of having the excerpts of other comments loaded as well. As a whole the output is unique.
I have tens of thousands of SEO blog comments URLs indexed over dozens of sites and I’m not seeing Google report duplicate content issues under Webmaster tools. The URLs also gain traffic in their own right from Google, so it seems Google likes the content (it is unique content).
David
