Depends on what you want this to do.

If you're looking for something to increase activity and such, a shop system would probably be better. Wasn't there a Zelaron RPG? You could tie in posts to generating game-money or something that would reward people for posting.

If you're looking for an epeen boost, this would just be a simple popularity contest, and add nothing at all to the site, it just puts numbers to things generally known. Definitely not worth the effort.

If you're looking to alert new members as to whom is regarded as a good poster, make this available only in sections like Life Discussion and such where people are looking for honest advice and assistance. That would help show people whose advice is often appreciated/etc.