If you want commentors to come and visit/comment on you blog often then use dofollow. Nobody likes nofollow. I will certainly like to comment on do-follow blog. Of course you shouldn't be selfish - give and take should be an equal.
for my new blog http://bloggingtruths.com comments are dofollow and also top commentators are awarded....but commenting requires registration and registered members are given gifts worth $500
I use Dofollow plug-in to protest the asinine and arbitrary nature of the whole nofollow concept, a link is a link and all of these fascist redirects, msplinks and nofollow is making the internet a harder to navigate place.
Hmmmmm... DoFollow? This has a positive and a negative on your blog. Last time, when I didn't applied these "DoFollow" on Blogging Kenneth, I do find less comment(s) to approve but when I applied it on and promoted the blog well, I do find it nice so that I won't have to do anything in return to those who are a part of it and I do find more spam which is also great. Because, it adds up to the current blog traffic I had.
Right from start I have keep TheCredence as Follow. I have never understood the concept of PR leak honestly! I can understand a PR6 blog home page link owner is worried about PR leak but WTH with a post which is not even crawled by google ? Of course keeping it as follow may make people to comment it as well, though don't expect flood of great comments
To dofollow your comment section can really help you boost participation on your blog, but be aware to have some anti-spam features up and running.
Ever see this: http://www.jyse.com/ ? It's a custom search engine for do-follow blogs and it's free to get your blog included.
Edit: OOOps...replied before I saw the post above mine...oh well. Here's a do follow search engine James
My blog is a do follow blog. A benefit besides increase in participation, is that you can add your blog to Do Follow lists which increases backlinks (a lot) and traffic.
I recently removed the nofollow atribute from my Game Videos blog. I can't report results because it was too recently.