won't this instigate an emphasis on quantity rather than quality posts?
i'd suggest using a "vote rating per post" (for lack of a better name for this)
i've seen it on conceptart.org, where readers can press a button next to a post, stating they "like" the post.
this can be for valuable information given, or an insughtful reply, or just because it's so funny i just spilled milk through my nose laughing.
dunno what type of systems are supported by this forum though..
in any event, it's nice to see you guys trying hard - and succeeding! - to constantly improve this haven to a bunch of overaged boys
