Submissions should hardly give any karma. That should take care of most of the problems regarding submissions.
About the approval: It should probably be the other way around. Flagged submissions are added to a queue for review (maybe letting the community to vote once more and therefor reviving the submission) and duplicates with comments are merged.
Random mumble: I have the feeling that many discussions depend too much on the poster. Sometimes complete discussions shift because of a comment of an established poster or live and die with said poster. And it's from time to time not because of some valuable insight but rather the fact that it's him/her. I am probably the only one who feels like that and I don't have a solution (if it needs one). Hiding the username and having to do an extra click (profile e.g.) to see who's behind the post would probably minimize the problem. But it would make it harder to filter out posts (which would need another indicator karma/per comment ratio (e.g.) to make it at least a bit useful).