IMO, the current ranking system is the best option for BPL at this point. The system encourages people to post, buy gear, and pay membership dues, which, in turn, helps the BPL community. It may not be an accurate measure of quality posting, user reviews, etc, but it does serve a purpose.
It would be a nightmare to attempt to discern the quality of individual posts, so that is not an option. Think of the labor that would be involved with such an endeavour.
One idea would be to use a system similar to what Practical Backpacking (better known as Bernie's Backpacking) utilizes. Bernie's system relies on fellow members to assign credibility to others. It appears nobody uses that option over there, so enough said on that.
Some people take things too seriously, and in that case, please ignore my post due to my low ranking! (haha)