goodroi - 11:00 pm on Apr 10, 2013 (gmt 0)
Have you ever looked to see if you have any referrals from those blog comments? Because if you have zero referrals from those blog comments, I would suggest you save yourself some time (and simplify your seo life) by no longer including your url.
Let's assume there are good reasons like relevant traffic & branding for you to post your url and gain nofollow links. It has been my experience that this is normally not an issue ASSUMING you have a significant amount of real dofollow links.
This can grow to be an issue and would make me nervous if 90% of your links were nofollow. High percentages are more likely to appear unnatural to Google and lead to trouble for you.