As I'm sure other Drupal webmasters can attest, despite best efforts, some comment spam still slips through and needs to be deleted manually. I've yet to figure out if this is from bots that have figured out how to break the captcha, or from humans who are adding the spam manually--but that's for another discussion.
What I wanted to post a wish for is the ability as webmaster to control more granularly whether or not the links within a comment use rel="nofollow". When a comment is new, it would be nice to have it use rel="nofollow", but then if I come along later and mark the comment somehow as "links approved", the rel="nofollow" would go away for that comment. I would prefer that this feature *not* be coupled to comment moderation.
The reason for requesting this particular design is that what happens is that some comment spam will slip in overnight while I'm sleeping. I delete it in the morning, but in the intervening hours, search engine bots have come along and indexed that page and added the spam keywords to the search index. So for several days after I have deleted the comment, the search engines are still sending porn and gambling searches to that page.
Another nice feature that would help in this area is a way to configure Drupal to reject a comment automatically if it contains more than a certain number of URLs pointing to a domain other than the "base URL." Most of the comment spam I get these days is packed with dozens of links, and a normal post would not contain that many links. It would be nice if Drupal were smart enough to help me with this. At least it would force the spammers to keep their comments shorter.