More unfortunately, there were still over 2000 comments (all of them spam) on the front page! I looked around and it turns out there's no way to bulk delete comments as of yet. And I sure wasn't going to sit there clicking more than 4000 times (one to delete, one to confirm). So I dug into the SQL and beat those bastards!
Anyway, in case anyone else runs into this problem, here's what I did: open up mysql and the first thing I found was that the root album had a g_id of 7. So I did these commands to first isolate the ID's of all the comments, and then delete them. There are probably better ways to do this but I'm a novice at this so I was aiming for safety...
CREATE TEMPORARY TABLE tmptable SELECT g2_Entity.g_id FROM g2_ChildEntity, g2_Entity WHERE g2_ChildEntity.g_id=g2_Entity.g_id AND g2_ChildEntity.g_parentId=7 AND g2_Entity.g_entityType='GalleryComment';
DELETE FROM g2_Comment, g2_Entity, g2_ChildEntity USING g2_Comment, g2_Entity, g2_ChildEntity, tmptable WHERE g2_Comment.g_id=tmptable.g_id AND g2_Entity.g_id=tmptable.g_id AND g2_ChildEntity.g_id=tmptable.g_id;
Hopefully this will be helpful to someone else, or at least a future version of myself :-)