I don't see any quality poster here neither is any one a bad poster (is just moderate or average). What matter is the area you find yourself, you can be a quality poster if you know what you are doing like for example, you are good in technical discussion people can find you quality, when you are good in bitcoin discussion people can find you quality, and as well as any section you can develop yourself more better.

I know there are people whose strength is to dig account and track people, i can assumed that is the area they knows better check them very well they hardly post in the gambling and any other section they don't know, while there are people who are also good in giving out forum data i can as well assumed that these people are good in that area.

So to sum it up, everyone is a quality/bad posters it all depends on the section you are contributing if it is helpful to the general public or not. I can also sets and example to does who are Pilots, and those who do Bike/motor racing they are good in what they do, everyone are professional in the field they knows more better, I can't condemn anyone and give preferences to others because others aren't good in their sections of contribution.
If you are not really convinced then you can used the bpip.org that gives you the overall list of people including; Most Merit, Most Activity, Most Trusted, Most Recognized people just as above user already suggested.