I know that you don't have intention to spam, but there are some blogs out there that have the dofollow attribute but are grouped along with those comments that don't contribute anything to the post, i.e. spam. You wouldn't want to be grouped with with those links. Anyway, to answer your question, there's a site that can help you find blogs with specific comment engines. Search for "dropmylink" on Google, and you'll see it on the top results. It helps you add the footprints that you would need in searching for different types of blogs.