Karma system would indeed give honest feedback regarding the user and the post count should be disabled in order to reduce trolling and worthless posts imo. There should be quality over quantity and would be nice if others see how much of your posts have really made difference and got good feedback from the community.
EDIT: I forgot to say that to change the system according to what the first post suggests is totally wrong, because rank has to/should show your contribution to forum. Trolling is not contribution.