Have you ever allowed blog comments in return for money or other favour ? Does it actually help in any way ?
I mean, what is there to loose ? Someone is going to spam anyway.
I see post exchange groups sometimes offer blog comments too. But if you are selling a space for links on your forum, better be in the blog post itself. If it fits well.
Whatever comes in the comment looks a bit spammy. That is simply the nature of blog comments, nothing purposeful.
What if we don't want to give too much weightage for those outgoing links ? Won't comments be a much proper place to add them ?