I found a PR4 .edu blog with auto-approve comments and a low OBL count - the most recent post only has 10 comments as of when I'm posting this! They're nofollow links, but an edu link is an edu link - still valuable. Just thought I'd share.
This is not "auto approve" in the traditional sense - it says "pending moderation" when you post, but from the experience of the Warriors who have added their link over the last day, it gets posted within an hour or so no matter what the quality is.
Don't spam it too hard