Retroactive commentspam removal?

Not to my knowledge, but it would be worth searching. You could include common spam words in the moderation word list and then check comments against that. That would at least take them out of public view and it would let you mark them all as spam with one click.

I’m not positive, but I think Spam Karma 2 has the ability to rescan all existing comments?

Check out Spam Nuker – won’t hurt to try
https://chrisjdavis.org/category/wp-hacks/

Spam Karma 2 does rescan the posts but isn’t always quite effective.

This is the correct URL for Spam Nuker, but it doesn’t really re-scan old comments, just delets them if they are already tagged as spam.

https://www.chrisjdavis.org/2005/03/05/spam-nuker-151/

Any other solutions out there?