Sure. One feature in phpBB and several other popular bulletin board packages (but not in reddit or Slashdot or any of their descendants) is the ability to set user titles: little snippets of descriptive text that get displayed after a user's handle and which are usually intended to give some information about their status in the forum.

The most common arrangement is to have a couple of special titles for administrative positions (say, "mod" and "admin"), then several others for normal users that're tiered based on the number of posts the user's written, i.e. postcount: a user might start with the title "newbie" or "lurker", then progress through five or six cutely themed titles as they post more stuff. It's common for admins to change the exact titles and the progression pattern to suit the needs of the forum (a roleplaying forum for example might name them after monsters of increasing power), but uncommon to change the basic scheme.

You may notice that this doesn't differentiate on post quality.