if you chose blog related to your blog and give decent comments then nothing going to be wrong but must every thing look real your comments and all the matter you write
A simple advice - enable the pre-moderation feature and manually delete all comments that lead to any inappropriate sites. And do not forget about links in your visitor's nicknames. Sometimes a harmless comment can have some child porn link in a nickname of person who left a comment.
thats interesting ... I mean really it s .... Ide do the same ..... dofollow is a pain ....then again hows got time to mod comments alday .