Its been gone over in detail lots of times in this thread, but its not practical to add a **************** checker. There are so many variables that you cannot possibly code something to keep up with millions of people making changes to the blogs that change the way **************** links work.
It would throw too many false negatives and the support quires that Sweet would receive about it would take so much time R&D would have to probably cease. Which would render us all dead in the water as things change.
You can use the link checker and just put the word nofollow in there instead of a website, but that will return only sites with the nofollow tag ANYWHERE on the page. Then whats left is ****************. So even if a footer link or whatever is nofollow. My tests on my hand verified lists shows as much as 70% false negative. Meaning 70% of **************** blogs that I could get a **************** comment link on, also had a nofollow link somewhere on the page, so they came back as nofollow.
So, basically use sbox to do everything but that and hand sort the really good quality ones, or just pepper them all and hope for the best.