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I hear the word 'cloak' and I immediately think 'bad'. Are you doing this in some way that won't get a site penalized? I'm genuinely curious.

Thank you for your answer people. It looks like index,nofollow would be indeed better. By looking more on the net, I also found a yoast article about this issue: http://yoast.com/wordpress-threaded-comments-and-seo/ "WordPress automatically adds a noindex, nofollow robots meta tag to each URL that has ?replytocom in it." This is why all my comments URL look like http://www.example.com/example-post/?replytocom=1 Yoast plugin update offers an option to remove ?replytocom variable. I think that I will have to drop All in one SEO on this website...

Thanks for your time, will do that.