I’ve just installed the Do Follow Trackback and Do Follow Comments plugins so now the links in your comments and trackbacks will be
stalked followed by Google and any other search engine or service that know about the
rel='nofollow' link attribute.
It’s not a completely free lunch though. Any spam comments will be deleted, legitimate comments with spammy urls will have their URLs mangled. Check out this comment and this one. Those _ characters in the urls make them pretty useless.
There are 7,457 comments on over 4,500 posts here. That’s a lot of URLs to get some PR loving.