OZH had one of those but the download link is dead: http://planetozh.com/blog/2005/02/wordpress-plugin-auto-moderate-comments/
I think I could use something like that, here is a description taken from that page:
Once installed and activated (see below), here is what the plugin does when someone posts a comment (or a trackback) to determine if this is Old Stuff® or not, and thus to accept the comment or send it to moderation queue :
Compare today’s date with date of last comment
If no comments, compare today’s date with post’s modification date
If never modified, compare today’s date with writing date
sounds great to me, should be simple to code, anyone supporting this request?
or do you consider this outdated? I think I'd love to use it.