If you are a responsible blogger, your blog will not contain any spam comments older than a certain age. You will usually delete the occasional one that slips past Akismet within at most a month, so anything older than that will have a 100% chance of being ham rather than spam.
So while it’s right and proper to include
rel="nofollow" on all hyperlinks in new comments, one would think it’s usually safe to remove it from older ones, and give constructive, bona fide comments on your blog some Google juice after a while. New comments should, of course, have the nofollow tag added.
I’m experimenting with this in the next version of Comment Timeout, which you can download and try out for yourself. The option is disabled by default, in which case all the comments on your website will, of course, be marked as nofollow, but you can of course turn it on if you want.
Another new feature is the option to indicate to your visitors how long comments will remain open on your blog.
Version 1.2 is currently in alpha, so it’s a case of “use at your own risk”, but I’m dogfooding it on my own blog, removing the nofollow on comments after 21 days. (NB: I make no guarantees that I won’t change the settings!) I’d be interested to know if anyone makes any use of it, or whether or not you think it’s a good idea. Let me know what you think by leaving a comment.
The current stable version is still 1.0 release candidate 2.
Update: I’ve released alpha 2, adding a bit more granularity to the nofollow options.