It's an interesting argument and one I'd not really thought about before. There is some sense in it - rather than have the conversation on your own blog - not allowing comments forces people to take it to theirs with links back to you. On the opposing side I think you'd find that a lesser percentage of people would do this than leave comments - thus in taking this approach you might build your own blog's ranking a little but you kill the potential conversations you might have.
I'm a massive fan of comments and value the learning that I do from interacting with my readers.
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About the Author:
Darren Rowse is the founder of ProBlogger.net, a blog about the many ways of adding an income stream to blogs.
Darren owns and writes a variety of blogs including Digital Photography Blog and Camera Phone
Zone. He is also a co-founder of the Breaking News Blog Collective.